CHEMURGIC 
CORPORATION 


§4. 


Book  I 

MODERN  GLUES  AND 
GLUE  TESTING 

(Other  than  Waterproof  Glues) 


BY 

CLYDE  H.  TEESDALE,  A.  B. 

Formerly  in  charge,  Section  of  Wood  Preservation,  Forest  Products 
Laboratory,  Madison,  Wisconsin 


With  an  Appendix 

Methods  of  Testing  Animal  Glues  at  the  Forest  Products  Labo- 
ratory, Madison,  Wis.,  in  which  is  set  forth  the  standards 
of  the  Bureau  of  Aircraft  Production,  U.  S.  Army 


Published  By 

THE  PERIODICAL  PUBLISHING  CO. 

GRAND  RAPIDS,  MICHIGAN 


Copyrighted  by 

The  Periodical  Publishing  Co. 

Grand  Rapids,  Michigan 

1922 


2031745 


PREFACE 

When  the  United  States  entered  the  great  war 
and  it  became  necessary  to  build  airplanes  by  thou- 
sands, very  definite  specifications  and  satisfactory 
methods  of  testing  glues  were  sorely  needed.  The 
problem  of  developing  specifications  and  methods  of 
test  was  turned  over  to  the  Forest  Products  Labora- 
tory and  was  worked  out  under  my  direction. 

This  book  is  based  largely  on  the  results  that 
were  obtained,  and  which  were  applied  in  practically 
all  purchases  of  glue  during  the  war  by  both  the 
Army  and  Navy  Departments.  General  information 
on  the  manufacture  and  use  of  glues  is  given,  and  a 
description  of  the  methods  of  testing  that  are  described 
in  the  literature  on  the  subject. 

Acknowledgement  is  made  to  Mr.  A.  T.  Deinzer  of 
Monroe,  Mich.,  who  contributed  valuable  information 
used  in  compiling  this  book;  also  to  Mr.  Geo.  M. 
Hunt  of  the  Forest  Products  Laboratory  for  valuable 
suggestions  and  criticisms  and  for  contributions  to 
parts  of  the  text,  and  to  Mr.  L.  J.  Markwardt,  Mr.  A. 
C.  Knauss,  and  Mr.  Wilbur  Lloyd  Jones,  of  the  Forest 
Products  Laboratory,  for  contributions  to  the  text. 

THE  AUTHOR. 


BOOK  I 

TABLE  OF  CONTENTS 
CHAPTER  I — General  Discussion — 

(Earliest  Record  of  Glues) — Distinction  between  Glues 
and  Gelatine — General  Process  of  Animal  Glue  Manu- 
facture— Resulting  Variation  in  Properties — Deter- 
mination— The  Peter  Cooper  Grades 11 

CHAPTER  II — Miscellaneous  Glues — 

Fish  Glues— Liquid  Glues— Vegetable  Glues— Casein 
Glues— Blood  Albumin  Glue— Silicate  of  Soda 15 

CHAPTER  III— Uses  of  Glue- 
Paper — Paper  Boxes — Books — Straw  Hats — Wall  Paper 
— Matches — Leather    Goods    and    Belting — Textiles — 
Writing  Tablets— Woodworking  19 

CHAPTER  IV— Glue  Testing  (Preliminary)— 

Preliminary  Examination — Absorption  of  Moisture 
from  the  Air — Appearance — Selecting  of  Samples — 
Surface  and  Other  Bubbles — Odor — Gloss — Color — 
Fracture — Foam — "Keeping"  Qualities 23 

CHAPTER  V—Glue  Testing— 

Evidence  of  a  Single  Test  not  Conclusive — Moisture — 
Ash — Acidity — Grease — Water — Absorption  —  Melting 
Point  27 

CHAPTER  VI— Viscosity— 

Types  of  Viscosimeters — Engler  Viscosimeter  the  U. 
S.  Government  Standard — Viscosity  Determination  at 
U.  S.  Forest  Products  Laboratory — Value  of  Viscosity 
Test  ..  31 


CHAPTER  VII— Jelly  Strength— 

The  Finger  Test — Lipowitz  Test — Edmund  S.  Smith 
Testing  Apparatus — Jerome  Alexander — Value  of 
Jelly  Strength  Test 37 


8 MODERN  GLUES  AND  GLUE  TESTING 

CHAPTER  VIII— Strength  of  the  Glued  Joint— 

Joint  Tests  Indicate  Quality  of  Workmanship  Rather 
than  Glue  Strength— Selection  of  Woods  for  Glue  Tests 
— Variation  in  Application  of  Glue  and  Manufacture  of 
Joint— Application  of  the  Load — The  Spandau  Test- 
British  Royal  Aircraft  Test — Aeronautical  Inspection 
—Directorate  (England)  Method— Shear  Test  and  Ten- 
sion Test— A  Widely  Used  Method  Discarded  at  Madi- 
son, Wis. — The  Forest  Products  Laboratory  Shear  Test 
—A  Modification  of  Madison  Standard  Test — Miscel- 
laneous Tests — Plaster  Rod  Test — Setterburg  Test — 
Gill  Test  41 

CHAPTER  IX— Plywood  Strength  Test— 

Equipment  and  Method  Adopted  as  Standard  at  the 
Forest  Products  Laboratory,  Madison,  Wis 57 

CHAPTER  X— Specifications— 

Bureau  of  Aircraft  Production,  U.  S.  Army — Specifica- 
tion for  Handling  and  Testing  Hide  Glue — U.  S.  Gov- 
ernment Standard  Specification  for  Hide  Glue  Certified 
in  Airplane  Construction 63 

CHAPTER  XI — Results  of  Tests  on  Miscellaneous 
Glues....  71 


CHAPTER  XII — Grading  the  Glue  Sample — 

Jerome  Alexander  and  Peter  Cooper  Grades  Compared 
—Table  of  Viscosities  and  Jelly  Strengths  for  Alex- 
ander Standard  Grades 77 

CHAPTER  XIII— Some    Interesting    Strength 
Data  on  Glues — 

Woods  that  give  Strong  Joints — Scratched  Joints 
versus  Smooth  Joints — Laminated  Construction — Re- 
sistance of  Animal  Glues  to  Moist  Air 81 

CHAPTER  XIV—  Use    and   Application    of    the 
Glue  Hydrometer 85 


APPENDIX. 

Methods  of  Testing  Animal  Glue  at  the  Forest  Prod- 
ucts Laboratory,  Madison,  Wis.,  1919  Standards  of  the 
Bureau  of  Aircraft  Production,  U.  S.  Army 87 


CHAPTER  I. 
GENERAL  DISCUSSION 

IT  is  said  that  glue  has  been  known  and  used  for 
thirty-three    hundred    years.      Furniture    found  EARLIEST 
in  tombs  of  the  ancient  Egyptians  of  the  period  RECORD  OP 
of  the  Exodus  was  dovetailed,  and  joined  with  glue  and  GLUES. 
nails.     Romans,  of  the  time  of  Cicero,  were  familiar 
with  glue,  and  it  was  in  extensive  use  in  England 
during  the  reign  of  Queen  Elizabeth. 

The  term  glue  is  used  in  its  broadest  sense  to  de- 
note an  adhesive.  Used  in  this  sense  it  includes  a  great 
variety  of  substances.  The  oldest  and  best  known  of 
these  is  animal  glue.  Animal  glue  comes  in  an  almost 
infinite  variety,  due  to  the  differences  in  methods  of 
manufacture  and  the  source  and  quality  of  the 
materials  used.  Glues  or  adhesives  are  also  produced 
from  starches,  casein,  blood  albumin  and  sodium 
silicate. 

In  general,  animal  glue  is  a  substance  akin  to  gela- 
tine, though  not  identical  with  it,  and  is  produced  from 
the  bones,  sinews,  hides,  etc.,  of  animals.    It  is  difficult  DISTINCTION 
to  define  the  difference  between  glue  and  gelatine  be-  BETWEEN 
cause  these  substances  may  be  very  similar  in  their  GLUES  AND 
composition,    appearance    and    properties.      Gelatine,  GELATINE. 
however,  is  usually  used  for  purposes  in  which  absence 
of  taste,  odor  and  color,  together  with  a  firmness  of 
jelly  are  desired.     It  is  often  used  in  foods.     Con- 
sequently it  is  prepared  from  selected  materials  free 
from    decomposition.     Glue,   on   the   other   hand,    is 
usually  used  for  its  adhesiveness,  and  lower  grade 
materials  and  less  care  may  be  employed  in  its  pro- 
duction. 

It  is  rather  important  for  a  glue  user  to  have  a 
clear  idea  of  the  difference  between  glue  and  gelatine 
and  of  the  method  of  manufacture  of  glue.  A  true 
conception  of  this  may  cause  him  to  change  his 
methods  of  glue  handling.  The  frequently  heard  state- 
ment that  gelatine  is  a  pure  form  of  glue  is  not  strictly 
correct.  Neither  glue  nor  gelatine  occurs  as  such  in 


12 


MODERN   GLUES  AND  GLUE   TESTING 


GENERAL 
PROCESS    OF 
ANIMAL   OLUE 
MANUFACTURE. 


VARIATIONS    IN 
METHODS  OF 
MANUFACTURE. 


nature.  They  are  formed  by  heating  certain  animal 
tissues  in  the  presence  of  water.  The  action  is 
chemical,  not  simply  one  of  solution.  A  portion  of  the 
water  molecule,  according  to  recent  ideas,  combines 
chemically  with  the  animal  matter,  the  technical  term 
describing  the  action  being  "hydrolysis."  This  action 
proceeds  rapidly  at  a  high  temperature,  and  slows 
down  as  the  temperature  is  lowered.  Hence  both  time 
and  temperature  are  important  factors  in  glue  making. 
As  the  action  proceeds,  a  series  of  products  is  formed, 
each  one  differing  slightly  from  the  one  from  which  it 
was  produced.  While  neither  glues  nor  gelatines  are 
produced  in  this  way  commercially,  we  may  consider, 
for  our  purpose,  that  the  first  one  formed  is  gelatine. 
Continued  action  produces  first  very  strong  viscous 
glue,  then  weaker  and  weaker  glues,  until  finally,  if 
the  action  is  continued  long  enough,  a  product  is 
obtained  that  will  not  form  a  jelly  when  cold,  and 
which  has  no  adhesive  properties.  It  makes  no 
difference  whether  the  heating  occurs  in  the  glue 
maker's  boiler  or  in  the  wood  user's  shop  room.  When- 
ever the  glue  is  heated  in  the  presence  of  water, 
chemical  action  occurs  which  steadily  reduces  the 
quality  of  the  product.* 

The  process  of  making  animal  glue  is,  briefly,  as 
follows:  The  stock  is  washed  and  treated  to  remove 
dirt  and  grease,  then  boiled  to  convert  the  glue-form- 
ing substances  into  a  glue  solution,  which  is  concen- 
trated by  evaporation  until  it  will  form  a  jelly  on 
cooling.  The  jelly  is  then  dried  and  the  resulting 
product  is  the  glue. 

There  are  many  details  and  variations  in  the  steps 
above  outlined  which  depend  upon  the  kind  of  stock 
used  and  the  plant  in  which  the  glue  is  made,  all  of 
which  have  more  or  less  effect  upon  the  character  of 
the  resultant  glue.  For  instance,  bones  are  sometimes 
boiled  without  first  removing  either  dirt  or  grease. 
This  naturally  fails  to  produce  a  high-quality  glue.  It 
is  common  practice  to  treat  bones  with  acid  to  remove 
the  calcium  salts  before  cooking,  but  this  is  not  always 
done.  In  cooking,  the  temperature  and  time  have  to  be 


*See  Rideal  (Glue  and  Glue  Testing),  page  10. 


GENERAL    DISCUSSION  13 

carefully  watched,  as  over-cooking  may  materially  re- 
duce the  strength  of  the  glue.  The  stock  is  usually 
boiled  several  times,  using  fresh  water  each  time.  .The 
first  boiling  or  first  run  gives  the  best  glue,  the 
strength  of  the  glue  obtained  from  the  succeeding 
boilings  being  less  each  time.  Sometimes  two  or  more 
boilings  from  the  same  kettle,  or  boilings  from  dif- 
ferent kettles,  are  mixed  together  or  "blended"  before 
the  liquor  is  concentrated. 

The  solution  of  glue  from  the  boiling  kettles  is  too 
weak  to  form  a  jelly  which  can  be  handled,  so  it  must 
be  concentrated.  This  is  done  by  boiling  off  the  water 
in  vacuum  pans  until  the  percentage  of  glue  in  the 
solution  is  high  enough  to  make  a  firm  jelly  on  cooling. 
If  the  temperature  gets  too  high  during  the  con- 
centrating process  the  quality  of  the  glue  may  be 
lowered. 

When  sufficiently  concentrated  the  glue  solution  is  METHODS  OF 
cooled  by  refrigeration,  either  after  being  run  into  COOLING. 
pans  or  as  it  runs  upon  a  traveling  belt.    As  it  cools 
it  forms  a  jelly  firm  enough  to  handle.    The  jelly  in  the 
pans  is  removed,  sliced  with  wires  or  a  knife,  and 
placed  upon  screens  to  dry.    If  a  belt  is  used  the  jelly 
is  formed  in  a  continuous  sheet,  which  is  cut  into  sec- 
tions and  placed  on  screens  as  it  travels  along.     The 
screens  are  then  placed  in  a  drying  chamber  and  left 
until  the  glue  is  dry.    The  glue  may  be  easily  injured 
during  the  drying  process  if  the  temperature  condi-  MISCELLANEOUS 
tions  are  not  properly  controlled.     The  form  of  the  FORMS.  OF 
glue  when  dry  depends  upon  the  shape  in  which  it  was  GLUE- 
placed  upon  the  screens.     If  carefully  sliced  to  the 
proper  thickness  regular  shaped  cakes  will  be  formed. 
The  sheet  glue  from  the  belt  breaks  into  thin  irregular 
shaped  pieces  as  it  comes  from  the  drying  nets.    This 
is  commonly  run  through  a  machine  to  break  it  into 
smaller  pieces,  in  which  shape  it  is  shipped  as  flake 
glue.        Other  miscellaneous  forms  of  glue  are  also 
made,  and  any  of  them  may  be  subsequently  ground 
and  sold  as  ground  glue. 

Sometimes  mineral  matter  such  as  barium  sulphate, 
white  lead,  chalk,  or  whiting  is  added  to  the  glue 
after  it  has  been  concentrated,  but  before  it  is  cooled. 


14 MODERN  GLUES  AND  GLUE  TESTING 

This  gives  it  a  light  color  and  makes  it  opaque,  which 
is  a  feature  desired  by  some  consumers. 

From  the  above  very  brief  description  of  various 
steps  in  the  manufacturing  process  it  can  readily  be 
seen    that    the    variety    in    character,    color,    fornj, 
strength,  etc.,  of  glues  can  be  almost  without  limit. 
PETER  COOPER     A  system  of  classification,  based  chiefly  on  the  jelly 
GRADES.  strength,  was  devised  a  long  time  ago  by  Peter  Cooper, 

by  which  it  is  possible  to  group  the  great  variety  of 
glues  into  a  relatively  few  classes  or  grades.  The 
grades  established  by  Cooper,  beginning  with  the 
strongest,  were  designated,  respectively,  A  Extra,  1 
Extra,  1,  IX,  1*4,  1%,  li/2,  1%,  %  17/8,  2.  There 
are  now  glues  stronger  than  A  Extra,  and  glues 
weaker  than  2,  for  which  there  is  no  standard  Peter 
Cooper  grade.  This  system  of  grading,  however,  ap- 
pears to  be  but  little  used  today  by  manufacturers, 
except  sometimes  for  comparative  purposes.  Each 
manufacturer  has  his  own  system  of  grading  which 
he  keeps  more  or  less  secret,  and  to  the  general  buying 
public  the  grades  mean  little  or  nothing.  It  is  some- 
times claimed  also  that  the  Peter  Cooper  grades  of 
today  are  not  the  same  as  those  established  long  ago. 


CHAPTER  II. 
MISCELLANEOUS  GLUES 

FISH  glue  is  made  from  the  skins,  bones,  bladders, 
etc.,  of  fish.     The  finest  grades  are  made  from 
the  swimming  bladders,  and  come  on  the  market  FISH 
in  the  product  known  as  isinglass.    It  is  said  that  fish  GLUES. 
glues  can  be  made  that  are  practically  equal  in  ad- 
hesiveness to  hide  or  bone  glues. 

Liquid  glues  are  marketed  in  liquid  form  ready 
for  use.    Most  glues  are  so  prepared  that  they  can  be 
used  cold.    They  are  quite  popular  and  have  a  large 
sale.    Usually  they  are  higher  in  price  than  ordinary  LIQUI1 
animal  glues.    They  may  be  prepared  by  special  treat-  G1 
ment  of  hide  or  bone  glue,  but  very  often  they  are 
made  from  fish  glues. 

In  recent  years  vegetable  glues  have  been  used  in 
increasing  quantities,   especially  for  gluing  veneers. 
At  the  start  of  the  war  the  price  of  animal  glue  soared, 
and    forced    a    very    wide    use    of    vegetable    glues,  STARCH 
especially  in  the  veneer  trade,  where  the  use  of  animal  GLUES. 
glues  was  practically  eliminated.    The  commercial  im- 
portance of  vegetable  glue  is  now  obvious  to  practically 
every  large  user  of  glue. 

Most  vegetable  glues  are  made  from  starch  and 
alkali.  Some  consumers  seem,  however,  to  be  suc- 
cessfully gluing  with  starch  boiled  in  water,  without 
the  addition  of  alkali.  The  most  commonly  used  veget- 
able glues  are  produced  from  cassava  flour  and  caustic 
soda  (sodium  hydroxide).  During  the  war  the  short- 
age of  shipping  facilities  prevented  the  importation 
of  cassava  flour,  and  much  potato  starch  was  used, 
usually  where  possible  in  mixtures  of  as  much  of  the 
cassava  flour  as  possible.  Corn  starch  has  been  used.  POTATO  STARCH 
Other  materials  than  caustic  soda,  such  as  tri-sodium  G 
phosphate,  sodium  carbonate,  etc.,  have  been  used. 
Sometimes  the  starch  is  treated  with  sulphuric  acid 
(hydrolized  or  processed)  before  mixing  with  the 
alkali.  The  best  qualities  of  vegetable  glues,  when 
properly  made,  show  strength  properties  which  com- 


16 


MODERN  GLUES  AND  GLUE  TESTING 


pare  favorably  with  the  medium  to  good  grades  of 
animal  glues.  They  also  have  certain  advantages  of 
use,  especially  that  of  applying  cold,  that  are  well 
known  to  most  of  our  readers.  Vegetable  glues  are 
often  criticised  because  of  their  rather  common  prop- 
erty of  staining  wood.  Recent  work  indicates  that  this 
difficulty  is  being  overcome. 

The  Perkins  Glue  Company,  well  known  manufac- 
turers of  vegetable  glue,  made  the  following  state- 
ment: 

PERKINS  "Vegetable  glue  is  manufactured  by  taking  a  car- 

GLUE.  bohydrate  such  as  cassava  flour,  the  water  absorptive 

property  of  which  has  been  decreased  or  is  already 
sufficiently  low,  but  not  too  low,  and  mixing  therewith 
the  necessary  small  amount  of  water  and  dissolving 
the  starch  in  the  water  by  stirring  in  a  solvent  such 
as  caustic  soda,  whereby  a  viscous,  colloidal  semi-fluid 
glue  is  formed  having  substantially  the  properties  of 
animal  glue  for  veneering.  Some  heat  may  be  used  in 
making  the  solution,  in  which  case  the  amount  of  alkali 
used  may  be  decreased." 

Ordinary  glues  were  not  equal  to  the  demands  of 
war  time  airplanes,  and  as  a  result  the  development 
of  waterproof  glues,  especially  for  veneer  parts  of  air- 
planes, received  a  tremendous  impetus  during  the  war. 
WATERPROOF       The  successful  airplane  waterproof  glues  were  all  made 
CASEINS  AND       either  from  casein  or  blood  albumin.    The  wide  use  of 
BLOOD  ALBUMIN  these  glues  in  the  industries  will  without  doubt  result 
GLUES.  after  the  war  in  their  widespread  adoption  for  in- 

dustrial purposes.  Not  only  may  they  replace  bone  or 
vegetable  glues  for  some  purposes,  but  they  make  pos- 
sible the  use  of  veneered  and  built-up  wood  products  in 
exposed  locations,  formerly  not  possible  because  of  the 
lack  of  a  suitable  glue. 

Casein  glues  in  general  are  made  from  ground 
casein,  calcium  hydrate  (slaked  lime),  and  some  form 
of  caustic  soda.  Sometimes  sodium  silicate  or  sodium 
phosphate  are  used.  Blood  albumin  glues  are  made 
usually  from  black  soluble  blood  albumin,  calcium 
hydrate,  with  a  small  quantity  of  sodium  silicate, 
sodium  hydrate,  or  ammonia.  Often  casein  is  mixed 
with  the  blood  albumin.  Casein  glues  set  hard  when 


MISCELLANEOUS    GLUES 17 

cold,  and  are  consequently  termed  cold  glues.  They 
may  be  used  in  cold  press  equipment.  Blood  albumin 
glues  depend  upon  the  application  of  heat  to  coagulate 
the  albumin,  and  hence  require  heated  presses  for  their 
application. 

Silicate  of  soda  is  successfully  used  as  an  adhesive 
in  the  paper  box  industry.     There  is  a  widespread  WATER 
feeling  that  it  may  some  day  be  used  to  advantage  in  GLASS. 
certain  lines  of  wood  work.    Without  doubt  the  very 
low  cost  of  silicate  of  soda  makes  it  an  attractive 
material  with  which  to  experiment,  and  the  results 
thus  far  obtained  are  promising. 

The    Bureau    of   Plant    Industry,    United    States 
Department  of  Agriculture,  has  patented  an  adhesive  CORN  OOB 
produced  by  boiling  corn  cobs  in  water  under  pressure.  ADHESIVE. 
The  resultant  solution  is  concentrated  and  used  as  an 
adhesive.     The  product  is  not  as  yet  developed  to  a 
commercial  success,  but  gives  great  promise  of  suc- 
ceeding as  a  substitute  for  sodium  silicate  in  the  paper 
box  industry.     It  is  said  that  it  will  be  lower  in  cost 
than  sodium  silicate. 


CHAPTER  III. 

USES  OF  GLUE 

GLUE  is  used  in.  a  great  variety  of  industries, 
aside  from  its  use  in  joining  wood.     Among 
these  may  be  mentioned  paper  sizing,  where  its 
purpose  is  to  make  the  surface  of  paper  less  porous, 
or  to  give  it  "glaze."    Animal  glue,  gelatine  and  casein 
are  used,  dependent  to  some  extent  on  the  relative 
market  costs  and  availability  at  the  moment,  and  upon 
the  quality  of  the  product  being  made. 

Glue  for  sizing  paper  is  usually  bone  glue,  of  high  PAPER 
grade,  free  from  foam,  light  in  color,  and  containing  SIZE. 
no  more  than  the  normal  amount  of  grease.    It  should 
show  no  perceptible  odor  after  heating  a  solution  in 
water  at  100°  F.  for  100  hours.    Alum  is  sometimes 
added  to  this  glue  by  the  paper  manufacturer  to  make 
a  free  flowing  solution. 

Paper  box  makers  prefer  a  quick  setting  hide  glue  PAPER  BOX 
for  "setting  up."    For  "covering"  a  slow  setting  bone  ADHESIVE. 
glue  is  used.    Mixtures  of  animal  glues  with  vegetable 
glues  are  often  used,  one  advantage  being  lower  cost. 

Here  a  product  is  required  that  is  strong,  flexible  BOOK 
and  free  from  color  and  odor.  BINDING. 

Straw  hat  manufacturers  desire  a  hide  glue  free 
from  lime,  color  and  odor. 

In  wall  paper,  freedom  from  grease  and  objection- 
able odor  is  desired. 

In  match  making,  uniformity  is  desirable.     The 
glue  is  used  in  combination  with  phosphorous  to  assist 
in    preventing    atmospheric    oxidation  of  the  phos-  MISCELLANEOUS 
phorous. 

For  leather  goods  and  belting,  flexibility,  tenacity 
and  resistance  to  moisture  are  the  desirable  qualities 
in  glue  for  leather  and  belting.  High  grade  hide  glues 
with  linseed  oil  and  glycerine  added  in  small  amounts 
are  often  used.  Glycerine  is  said  to  increase  flexibility, 
and  linseed  oil,  resistance  to  moisture. 


20 


MODERN  GLUES  AND  GLUE  TESTING 


JOINING 
WOOD. 


HIGH   GRADE 
GLUE    MAY    BE 
THE  MOST 
ECONOMICAL. 


USED  IN  Glue  is  used  in  dressing  and  finishing  colored  yarns 

TEXTILES.  and  threads,  sizing  of  worsted  and  woolen  wraps,  and 

in  the  printing  of  fabrics.  High  grade  hide  glues  free 
from  odor  and  color  are  required. 

Tons  of  glue  are  used  for  writing  tablets.  Almost 
any  grade,  except  the  very  poorest,  will  answer. 

A  glue  is  valued  primarily  for  its  power  of  resist- 
ing rupture.  This  includes  absence  of  brittleness,  and 
it  should  have  the  power  of  yielding  or  stretching 
slightly  before  it  ruptures.  Glues  may  be  found  which 
are  very  strong  if  the  strain  is  applied  steadily,  but 
which  break  under  the  impact  of  a  suddenly  applied 
load.  A  weaker  b,ut  more  elastic  sample  is  superior 
to  such  a  glue  for  joining  wood.  In  general  however,  a 
glue  may  be  valued  on  a  basis  of  its  strength  proper- 
ties. 

Intimately  related  to  the  strength  property  is  the 
covering  capacity  of  glue.  Its  value  is  largely  con- 
trolled by  these  two  factors.  High  strength  usually  is 
accompanied  by  great  covering  capacity,  and  hence 
higher  priced  glues  may  actually  cost  less  to  use  than 
lower  priced  ones,  which  require  more  glue  to  ac- 
complish the  same  purpose.  Covering  capacity  is  re- 
lated to  three  factors — the  water  absorption,  the  jelly 
strength,  and  the  viscosity  of  a  solution  of  known 
strength.  These  tests  made  with  accuracy  will  usually 
give  a  close  indication  of  the  grade  or  the  value  of  a 
glue. 

Color  is  important  in  some  lines  of  wood  work, 
being  especially  undesirable  in  high  grade  furniture. 
As  a  rule,  however,  a  dark  color  should  not  be  con- 
sidered detrimental,  as  absence  of  color  may  represent 
high  cost  or  the  use  of  undesirable  and  weakening 
chemical  bleaching  agents. 

KEEPING  Keeping  qualities  are  of  some  importance.  Alkaline 

QUALITY  OF         glues  are  more  liable  to  spoil  or  decompose,  due  to 
GLUES.  bacterial  action,  than  acid  glues.     Hence  a  test  for 

acidity  and  alkalinity  give  an  indication  of  keeping 
properties.  Glues  made  from  partly  decomposed  stock 
do  not  keep  well,  and  have  a  bad  odor  when  the  glue 
solution  is  heated.  Hence  odor  has  a  bearing  on  keep- 
ing qualities. 


USES   OF   GLUE  21 

A  recent  development  is  the  use  of  glue  as  a  filler 
in  automobile  tires.     The  lower  grades  of  bone  glue 
that  formerly  went  largely  to  the  veneer  trade,  are 
preferred.    This  new  use  of  glue  is  of  tremendous  im-  AUTOMOBILE 
portance  to  the  animal  glue  industry,  especially  in  view  TIRES- 
of  the  inroads  made  on  their  market  by  vegetable  glues. 
At  the  present  time,  only  a  few  tire  concerns  are  using 
glue,  but  the  demand  from  this  source  promises  to 
expand  to  very  large  proportions. 


CHAPTER  IV. 

GLUE    TESTING     (PRELIMINARY) 

A  UNIFORM   and   generally   adopted   method   of 
testing   glue   has    never   been    developed,    due 
largely  to  the  variable  and  uncertain  chemical 
composition  of  glue.     It  is  exceedingly  desirable  for  GLUE  TESTING 
glue  users  to  test  their  glues  rather  than  trust  wholly  REQUIRES  A 
to  the  promises  of  the  salesman.     The  technique  of  SKILLED 
glue   testing   requires   a   trained   observer   and    good  OPERATOR. 
equipment  to  accomplish  very  much,  though  there  are 
a  few  simple  tests  and  observations  that  can  be  made 
by  any  one  and  which  will  give  some  idea  of  quality. 

Chemical  analysis  of  glue  does  not  enable  one  to 
select  glues  according  to  quality,  and  has  never  been 
successfully  applied.  Glue  testing  consists  largely  of 
physical  tests,  such  as  viscosity,  jelly  strength, 
strength  of  the  glued  joint,  ash,  moisture,  odor,  etc. 

War  made  necessary  the  development  of  methods  of 
testing  and  specifying  glue,  and  centered  the  attention 
of  experts  in  this  kind  of  work  on  the  glue  testing 
problem,  not  only  in  the  United  States,  But  in  the 
European  countries.    The  glue  testing  methods  selected 
by  the  warring  countries  were  naturally  the  best  avail- 
able, and  hence  are  worthy  of  the  most  serious  con- 
sideration of  any  reader  interested  in  this  subject. 
One  of  the  most  successful  attempts  thus  far  made  to  GLUE  TESTING 
develop  a  uniform  practice  of  glue  testing  was  ac-  SCIENCE 
complished  in  the  United  States,  where  all  glues  for  ADVANCED  BY 
airplanes  for  both  the  army  and  navy  was  given  a  THE  WAR- 
most  thorough  inspection.    This  work  was  done  at  the 
Forest  Products  Laboratory  at  Madison,  Wis.    Inten- 
sive investigation  by  a  large  force  over  several  months 
on  methods  of  testing  was  carried  out  under  the  guid- 
ance of  a  glue  chemist  of  national  reputation.    All  of 
the  testing  methods  that  might  seem  to  have  any  merit 
whatsoever     were     tried.       The     resultant     methods  TESTS  BY  AN 
selected  in  this  way  were  incorporated  in  a  tentative  AUTHORITY. 
specification  which  was  submitted  to  a  conference  of 
glue  manufacturers,  and  as  finally  evolved,  had  the 


24 


MODERN  GLUES  AND  GLUE  TESTING 


SOME 

SIMPLE  BUT 
SUPERFICIAL 

TESTS. 


SIGNIFICANCE 
OF  COLOR. 


approval  of  all.  They  may  therefore  be  considered  as 
the  best  that  this  country  has  developed  thus  far. 

In  the  following  pages  a  few  simple  tests  will  be 
outlined  that  are  possible  to  make  without  great  ex- 
perience or  complete  equipment.  The  more  refined 
tests,  however,  require  a  trained  analyst,  familiar  with 
the  manipulation  of  testing  apparatus,  and  a  well 
equipped  laboratory.  The  methods  of  test  recom- 
mended by  the  Forest  Products  Laboratory  are  men- 
tioned in  outline  only  in  the  text,  but  are  grouped 
together  and  given  in  full  in  the  appendix. 

Glue  should  not  become  damp  or  sticky  (hygro- 
scopic) in  the  air,  or  it  may  mold.  A  hygroscopic  glue 
indicates  adulteration  with  sugar,  molasses,  etc.  The 
appearance,  hardness  and  manner  of  breaking  are 
points  which  may  be  used  to  judge  quality  after  some 
experience.  Some  glues  may  have  a  cloudy  or  milky 
appearance,  due  to  the  presence  of  calcium  phosphate. 
Glues  of  excellent  strength  may  be  warped  or  twisted, 
and  very  dark  in  color.  Ground  glue  should  not  lump 
together  in  warm,  humid  weather. 

Samples  should  be  taken  from  several  parts  of  the 
package,  as  glues  are  very  often  blended  from  more 
than  one  run  and  the  mixing  may  not  have  been 
thorough.  Special  attention  should  be  given  ground 
glue,  which  is  very  easy  to  adulterate.  White  bubbles 
on  the  surface  of  the  glue  are  an  indication  of  decom- 
position. With  such  samples  be  sure  to  test  the  odor, 
as  described  later.  Decomposed  or  sour  glues  are  to 
be  avoided.  Bubbles  appearing  deep  in  the  glue  are 
not  necessarily  an  indication  of  putrefaction.  An 
expert  glue  buyer  is  able  to  judge  somewhat  by  ex- 
amining a  flake  of  glue  by  looking  through  it  at  a 
strong  light. 

Gloss  on  the  surface  does  not  necessarily  indicate 
high  quality.  On  the  contrary,  low  grade  glues  may 
be  highly  glossed,  while  good  quality  glues  may  be 
dark,  though  the  surface  should  be  smooth.  A  uni- 
form color  and  surface  appearance  is  desirable. 

Color  is  not  a  reliable  indication  of  quality.  The 
first  runs  of  glue  from  the  glue  stock  are  lighter  in 
color  than  the  last  ones.  But  it  is  easy  to  clarify  glues 


GLUE  TESTING  (PRELIMINARY)     25 

chemically,  greatly  weakening  them  in  the  process. 
Bone  glues  are  usually  darker  than  hide  glues,  unless 
they  have  been  bleached.  With  any  particular  lot,  non- 
uniformity  of  color  indicates  either  adulteration  or 
blending.  The  addition  of  zinc  oxide  gives  a  white 
opaque  glue,  and  one  that  sets  quickly.  It  is  also  said 
to  add  somewhat  to  its  water  resistance.  In  moderate 
quantities  zinc  oxide  is  not  injurious.  Sometimes  inert 
matter  of  no  value  is  added  as  an  adulterant.  Hence 
the  color  of  such  samples  may  well  be  reason  for 
suspicion. 

Breaking  a  sample  of  the  glue  with  the  thumb  and  SIMPLE  TEST 
forefinger  of  each  hand  gives  an  indication  of  glue  FOR  QUALITY. 
quality.    The  condition  of  the  air  must  be  considered, 
as  a  dry  day  will  give  a  different  indication  than  a 
humid  one.     If  the  glue  fractures  evenly  and  bends 
but  little,  low  strength  and  brittleness  are  indicated. 
If  a  thin  sheet  bends  well  and  in  case  it  breaks,  shows 
a  splintery  fracture,  good  strength  is  indicated.    Bone 
glues  show  a  glossy  fracture ;  hide  glues  of  high  grade 
never  do. 

Foam  in  a  glue  is  undesirable.  A  solution  of  glue 
in  water  may  be  stirred  vigorously,  with  a  rod,  or 
better,  with  an  egg  beater,  and  a  fair  indication  of  its 
foaming  properties  will  be  obtained.  Particular  atten- 
tion should  be  paid  to  the  rate  at  which  the  foam  sub- 
sides. If  it  persists  for  long,  the  glue  should  be 
avoided. 

Odor  is  a  sign  of  poor  keeping  quality.     Usually  ODOR  SHOULD 
offensive  odor  is  the  result  of  using  spoiled  or  de-  BE  SWEET. 
composed  stock,  or  else  it  may  mean  that  the  glue  itself 
has  started  to  decay. 

Something  may  be  learned  by  smelling  of  a 
moistened  flake  of  glue  warmed  in  the  hand.  A  more 
reliable  method  is  to  heat  a  solution  of  glue  in  water, 
about  1  part  glue  to  12  of  water,  at  a  temperature  of 
100°  for  48  hours.  It  should  remain  sweet  during  this 
period.  A  similar  sample  should  be  able  to  stand  at 
room  temperature  for  four  or  five  days  without  de- 
veloping a  bad  odor,  or  showing  the  presence  of  mold 
or  decomposition. 


CHAPTER  V. 

GLUE    TESTING* 

WHILE  the  tests  just  described  are  useful  guides 
in  purchasing  glue  in  the  absence  of  better 
methods,    they    are,    at    best,    a    makeshift. 
Wherever  possible  advantage  should  be  taken  of  more  TESTg  ARE 
refined  methods.  MISLEADING. 

The  reader  should,  however,  have  a  rather  clear 
idea  of  the  limitations  of  glue  testing.  It  is  usually 
not  possible  to  obtain  a  very  clear  idea  of  glue  value 
from  any  single  test  that  may  be  applied.  In  an  article 
describing  the  testing  and  grading  of  glues,  the  follow- 
ing statement  is  made  by  E.  G.  Clayton  (Jour.  Soc. 
Chem.  Ind.,  1902,  21,  670) : 

"In  conclusion,  the  observations  seem  to  show  that 
while  it  would  be  rash  to  form  a  judgment  on  glue 
from  a  single  test,  the  evidence  afforded  by  a  number 
may  be  irresistible.  The  expert's  surest  system  ap- 
pears to  be  not  to  rely  on  single  short  cut  tests  of 
general  quality,  but  to  employ  a  number  of  methods, 
including  any  having  especial  bearing  on  the  pros- 
pective or  present  uses  of  the  glue,  and  then  to  base 
his  conclusions  on  a  consideration  of  all  the  results 
together." 

Ordinary  glue  of  good  quality  contains  from  8  to 
16  per  cent,  of  water.    Too  much  water  indicates  poor  MOISTURE 
keeping  quality,  and  of  course  means  that  the  buyer  D 
is  paying  for  that  much  water.    Too  little  water  may 
indicate  an  over-dried  glue,  which  is  injurious  to  its 
strength  properties.     Moisture  as  low  as  5  per  cent, 
is  not  uncommon,  but  a  good  glue  should  have  not 
less  than  8  per  cent. 

Moisture  is  determined  by  heating  a  ground  sample 
at  a  temperature  of  110°  C.  to  a  constant  weight.  The 
sample  being  hygroscopic,  must  be  cooled  in  a 
desiccator. 

After    making   the    moisture    determination,    the  DETERMINATION 
same  sample  may  be  used  for  determining  ash.     It 


*See  Appendix  for  Forest  Products  Laboratory  methods. 


28 


MODERN  GLUES  AND  GLUE  TESTING 


REACTION*  TO 
LITMUS. 


INSOLUBLE. 


WATER 
ABSORPTION*. 


should  be  incinerated  carefully  in  platinum,  or  pre- 
ferably in  vitreosil,  care  being  taken  to  prevent  free 
ignition.  The  ash  usually  varies  from  11/2  to  3  per 
cent.  A  fused  ash  indicates  a  bone  glue,  one  not  fused 
a  hide  glue.  A  large  ash  indicates  adulteration,  and 
a  chemical  examination  will  show  what  it  is.  Calcium 
phosphate  is  found  in  the  ash  of  bone  glues. 

By  its  reaction  to  litmus  a  glue  shows  whether  it 
is  acid,  alkaline  or  neutral.  The  test  is  made  by  dip- 
ping strips  of  red  and  blue  litmus  paper  in  a  glue 
solution,  and  noting  the  color  change.  (The  solution 
left  after  the  viscosity  test  may  be  used.)  An  acid 
glue  turns  blue  litmus  red,  and  a  neutral  glue  will  not 
change  the  color  of  either  red  or  blue  litmus.  Alkaline 
glues  will  turn  red  litmus  blue.  A  slightly  acid  glue 
is  preferable  to  a  neutral  or  alkaline  glue,  because  it 
is  not  quite  so  favorable  a  medium  for  the  growth  of 
the  organisms  which  cause  the  decay  of  glue.  Strong 
alkalinity  usually  means  an  over-limed  glue,  which  will 
almost  surely  cause  trouble. 

To  determine  insoluble  matter  dissolve  30  grams 
of  glue  in  one  liter  of  hot  water,  and  allow  to  stand 
for  12  hours  in  a  warm  place.  Filter  the  hot  solution 
through  a  weighed  filter  paper  or  good,  crucible,  wash 
well  with  hot  water,  dry  and  weigh.  In  hide  glues 
the  insoluble  matter  is  rarely  over  2  per  cent.  In  bone 
glues  it  may  be  more. 

A  little  aniline  color  is  added  to  the  solution  of  glue 
in  water  (some  of  the  solution  remaining  from  the 
viscosity  test  may  be  used).  The  mixture  is  painted 
on  unsized  white  paper  and  the  appearance  noted. 
Grease  is  visible  in  round,  characteristic  spots,  and  the 
relative  amount  present  is  indicated  by  comparison 
with  other  glues  or  the  experience  of  the  operator.* 

The  water  absorption  test  was  proposed  by  Schat- 
termann  in  1845.  Glue  does  not  dissolve  in  cold  water, 
but  has  the  property  of  absorbing  several  times  its 
weight  of  water.  Some  glues  will  absorb  eight  to  ten 
times  their  weight  of  water  and  still  retain  a  rather 
firm  consistency.  Good  glues  will  absorb  at  least  six 


*See  Jour.  Soc.  Chem.  Ind.,  Feb.  28,  1906. 


GLUE   TESTING  29 

times  their  weight.  A  method  used  by  the  United 
States  Bureau  of  Chemistry  is  as  follows:  Place  10 
grams  of  the  sample  broken  in  small  pieces  in  a  beaker 
and  cover  with  200  c.  c.  of  water  at  15°  C.  Cover  the 

11  11  •  e    •  j?         n  *.    i  -.LI      SIGNIFICANCE 

beaker  and  place  in  a  refrigerator  for  24  hours,  with  OF  THE  TEST 

the  temperature  between  14°  C.  and  18°  C.    Then  pour 

off  the  water  and  weigh  the  glue.    This  determination 

cannot  often  be  made  above  20°  C.     The  firmer  the 

jell  the  greater  the  glue  strength  (in  general),  and  the 

more  water  that  is  absorbed  the  greater  the  covering 

capacity  of  the  glue.    If  the  glue  becomes  slimy,  or  if 

the    solution    shows    evidence   of    putrefaction,    poor 

quality  is  indicated. 

The  melting  point  of  the  glue  solution  is  of  interest 
as  it  is  a  measure  of  how  quickly  or  slowly  the  glue 
will  set.  It  is  sometimes  used  as  a  substitute  for  the  MELTING 
viscosity  test.  The  test  is  sometimes  made  as  follows :  POINT- 
Weigh  15  grams  of  the  sample  and  soak  12  hours  in 
a  flask  with  30  c.  c.  of  water.  Then  immerse  the  flask 
in  boiling  water  and  shake  well  until  the  glue  dissolves. 
While  still  liquid  pour  some  of  the  solution  into  a  test 
tube  and  close  the  end  with  a  cork,  and  cool  for  one 
hour  in  water  at  15°  C.  Now  place  in  a  water  bath  in 
an  inclined  position,  with  a  thermometer,  and  gradu- 
ally raise  the  temperature.  When  the  glue  leaves  its 
vertical  position  the  temperature  may  be  taken  as  the 
melting  point. 

A  simpler  and  more  accurate  method  is  in  use  at 
the  Forest  Products  Laboratory.    A  drop  of  the  liquid      NEW 
glue  solution  is  run  into  a  glass  U  tube  of  small  size.  MELTIXG 
The  tube  is  then  cooled  in  water  for  10  minutes  at  15°  POINT  TEST. 
C.    It  is  then  placed  in  a  water  bath  and  the  tempera- 
ture raised  gradually.     The  melting  point  is  taken  as 
the  temperature  at  which  the  slug  of  glue  moves  down- 
ward in  the  U  tube. 

For  information  in  the  literature  on  the  melting 
point  determination  see  R.  Kissling  (Chem.  Zeitung, 
1901,  25,  264  and  Jour.  Soc.  Chem.  Ind.,  1901,  21,  509), 
also  N.  Chercheffsky  (Chem.  Zeitung,  1901,  25,  413, 
and  Jour.  Soc.  Chem.  Ind.,  1901,  25,  731). 


CHAPTER  VI. 
VISCOSITY 

THIS  test  is  one  of  the  most  important  of  the 
tests  made  on  glue,  and  is  in  universal  use  by 
glue     manufacturers.        (See     Fels,     Chemical 
Zeitung,  1898,  9,  also  Jour.  Soc.  Chem.  Ind.,  1890,  p. 
654.) 

Viscosity  is  a  term  used  to  describe  the  degree  of  TYPES  OF 
fluidity  of  the  glue  solution.    The  thicker  the  solution  VISCOSIMETERS. 
the  higher  its  viscosity  and  the  lower  its  fluidity  or 
flowing  power.     Instruments  for  measuring  viscosity 
(viscosimeters)   are  of  various  kinds.     Those  usually 
used  for  glue  testing  are  of  the  orifice  type,  and  depend 
in  principle  upon  the  time  required  for  the  passage  of 
a  known  quantity  of  liquid  through  a  standardized 
orifice,  at  a  known  temperature. 

Any  viscosimeter  of  the  orifice  type  may  be  used. 
Fels  used  a  modified  Engler  (Jour.  Soc.  Chem.  Ind., 
1890,  p.  654),  with  a  15  per  cent,  solution  (15  grams 
of  glue  in  100  c.  c.  of  solution).  Rideal  preferred  a 
type  described  by  Slotte  and  modified  as  described  in 
the  Journal  Society  Chemical  Industry,  1891,  page  615. 
A  later  modification  is  described  by  Scarpa  (Gazetta 
Chemica  Italiana,  1910).  Some  observers  express  vis- 
cosity in  the  number  of  seconds  required  for  the  glue 
solution  to  pass  through  the  orifice  of  the  apparatus. 


-5£  *£   dps 

S.S  g  «go      -°>  .-^-2^. 

r2                        Description  of                   °  v,  3  »o®<9  *•  2  «>  *J 

S6                           Samples                           ||  |     M  g.S  ||S 

1.  Light  yellow   transparent  thick  ' 

plates    163  149  1.65 

2.  Brown  transparent  glue 14.0  125  1.36 

3.  Sherry  yellow  transparent  glue     15.4  171  1.91 

4.  Light  yellow  plates 18.2  150  1.60 

5.  Muddy    (truber  glue) 15.2  199  2.21 


32 


MODERN  GLUES  AND  GLUE  TESTING 


A  POPULAR 
RAPID  TYPE  OF 
VISCOSIMETER. 


Others  prefer  to  express  it  as  the  ratio  between  the 
time  required  for  the  glue  solution  to  pass  through  the 
orifice  compared  with  water  at  the  same  temperature. 
Fels,  with  a  15  per  cent,  solution  at  30°  C.,  obtained 
the  results  shown  in  the  table  on  page  31. 

Other  workers,  using  different  instruments,  ob- 
tained different  figures.  The  value  obtained  depends 
upon  the  form  of  the  apparatus  and  the  size  of  the 
orifice. 

For  comparative  purposes  only,  a  home  made  de- 
vice may  be  used. 

One  may  be  made  from  a  volumetric  pipette,  fitted 
with  a  stop  cock.  The  lower  end  is  heated  in  a  glass 
flame  and  carefully  reduced  in  size  until  its  inside 
diameter  is  of  the  desired  size.  One  recommended  by 
Jerome  Alexander  (Jour.  Soc.  Chem.  Ind.,  1906,  p. 
159)  is  made  from  a  45  c.  c.  pipette,  and  will  pass  45 
c.  c.  of  water  at  80°  C.  in  15  seconds.  It  has  the  follow- 
ing dimensions: 

Capacity,  45  c.  c.  of  water  at  80  degrees  C. 

Internal  diam.  of  effluent  tube 6     mm. 

External  diam.  of  effluent  tube 9     mm. 

Length  over  all  of  effluent  tube 7     cm. 

Smallest  diam.  of  outlet  (about) 1.5mm. 

Outside  diam.  of  bulb 3     cm. 

Length  of  bulb 9.5  c. 

Length  of  upper  tube 22     cm. 

This  pipette  is  surrounded  with  a  water  bath,  and 
the  flow  of  solution  is  controlled  with  a  pinch  cock  and 
rubber  tube  fitted  over  the  top. 

Some  glue  factories,  where  a  great  many  samples 
have  to  be  tested  every  day,  use  a  more  rapid  home 
made  apparatus,  with  an  orifice  so  large  that  the  glue 
solution  will  pass  through  in  10  or  15  seconds.  One 
can  be  made  from  a  pipette  as  described,  or  from  a 
glass  tube  contracted  at  one  end.  For  several  reasons 
such  instruments  are  seldom  very  accurate. 

Better  control  of  temperature  and  greater  accuracy 
can  be  had  with  the  Engler  viscosimeter.  This  is 
more  complicated  and  more  expensive  than  the  pipette 
or  glass  tube  type,  and  is  also  slower  to  operate,  but  it 


VISCOSITY 


33 


GREASE  RECORD 


Date. 


Index  No.. 


Glue 


NOTE 

Grease  is  not  of  necessity  a 
serious  defect  in  Glue,  except  in 
certain  specific  uses.  It  does  reduce 
foam  and  affects  adhesiveness. 


Normal 


The  white  spots  show  the  grease. 
O  is       Free  of  Grease. 

5  and  under  is     Commercially  Free 

6  to    20          "       Normal 

21  to  35          "       Slight  Excess 

36  to  50          "       Excess 

51  and  over    "       Very  Greasy 


Examining  Chemist 


The  amount  of  grease  in  the  glue  is  indicated  by  the  light  spots. 
This  sample  is  "Normal." 


34 


MODERN  GLUES  AND  GLUE  TESTING 


GREASE  RECORD 


Date. 


Index  No. 


Glue 


NOTE 

Grease  is  not  of  necessity  a 
serious  defect  in  Glue,  except  in 
certain  specific  uses.  It  does  reduce 
foam  and  affects  adhesiveness. 


Very 
Greasy 


The  white  spots  show  the  grease. 
0  is       Free  of  Grease. 

5  and  under  is     Commercially  Free 

6  to    20          "       Normal 

21  to  35          "       Slight  Excess 

36  to  50  Excess 

51  and  over    "       Very  Greasy 


Examining  Chemist 


The  large  number  of  white  spots  shown  in  this  sample  indicate 
"Very  Greasy"  glue. 


VISCOSITY 35 

has  the  advantage,  in  addition  to  greater  accuracy,  of 
being  an  instrument  which  is  in  general  use  for  testing 
many  kinds  of  materials.    The  values  obtained  by  its  EXGLER 
use  are  readily  understood  by  laboratory  men  and  can  VISCOSIMETER 
be  readily  checked.    It  can  be  purchased  from  supply  is 
houses  standardized  and  ready  for  use.     The  Engler  RECOMMENDED. 
viscosimeter  is  in  use  at  the  Forest  Products  Labora- 
tory, and  is  required  by  the  specifications  for  glue  of 
the  army  and  navy.    It  is  recommended  for  standard- 
ized work  on  glues. 

The  viscosity  determination  is  made  at  the  Forest 
Products  Laboratory  as  follows :  One  part  of  glue  by 
weight  is  dissolved  in  5  parts  of  distilled  water  by 
weight.  The  sample  is  strained  to  remove  insoluble 
matter,  and  the  viscosity  determined  in  an  Engler 
viscosimeter  within  five  minutes  after  the  sample  has 
been  melted.  The  viscosity  is  expressed  in  terms  of 
the  number  of  seconds  required  for  200  c.  c.  of  glue 
solution  at  a  temperature  of  60°  C.,  to  pass  through  the 
standard  orifice  of  the  viscosimeter,  compared  with 
distilled  water  at  the  same  temperature. 

The  precaution  of  straining  the  glue  before  testing 
should  not  be  overlooked.  Insoluble  matter  may  clog 
the  orifice  and  materially  affect  the  result. 

The  viscosity  test  is  of  great  value  in  grading  glues,  SIGNIFICANCE 
and  is  one  of  the  most  important  tests  that  is  used.  OF  VISCOSITY 
In  general,  viscosity  is  a  gauge  of  glue  strength,  high  TEST. 
viscosity  corresponding  to  high  strength.     It  would 
lead  to  great  error,  however,  if  complete  reliance  were 
placed  on  the  results  of  this  test.     It  should  only  be 
considered  in  conjunction  with  other  tests.    Glues  pro- 
duced from  the  same  stock,  under  identical  conditions, 
may  be  graded  on  the  viscosity  test.    But  glues  under 
test  may  have  been  produced  from  different  stocks 
by  different  methods.     Hence  considerable  error  may 
be  found  by  relying  on  viscosity  alone. 

Acid  treated  bone  glues  give  viscosities  very  low 
in  proportion  to  their  jelly  strength.  Opaque  and 
colored  glues  give  higher  viscosities  than  clear  ones  of 
corresponding  strength.  Glue  stock  incompletely 
washed,  or  over-limed  gives  a  high  viscosity.  Some 
clarified  glues  have  a  low  viscosity,  both  bone  and  hide. 


36  MODERN  GLUES  AND  GLUE  TESTING 

Or  if  clarified  with  alum,  the  viscosity  will  be  too 
high.  Rabbit  glues  are  liable  to  have  viscosities  that 
are  too  high  to  correspond  with  their  jelly  strength. 
The  apparatus  used  may  also  lead  to  slight  errors,  as 
glues  do  not  always  grade  the  same  when  tested  with 
different  instruments. 


CHAPTER  VII. 

JELLY  STRENGTH 

ONE  of  the  most  significant  and  important  of 
the  tests  commonly  made  on  glue  is  an  esti- 
mation of  jelly  strength.  It  was  suggested  by 
Lipowitz  in  1861  and  has  been  extensively  adopted.  It 
is  made  on  a  solution  of  the  glue  in  water  cooled  to  a 
jelly  in  a  refrigerator,  and  consists  in  an  estimation 
of  the  strength  or  firmness  of  the  jelly.  In  spite  of 
numerous  attempts  to  develop  apparatus  for  obtaining 
a  measure  of  jelly  strength  in  terms  of  some  tangible 
numerical  unit,  the  finger  test  is  still  favored  by  those 
most  expert.  The  finger  test  is  akin  to  tea  or  wine 
tasting  in  that  it  requires  long  experience  and  great 
skill  to  obtain  good  results.  THE  FINGER 

The  finger  test  is  made  on  a  25-gram  sample  soaked  TEST  FOR  JELLY 
in  300  c.  c.  of  water  at  room  temperature.  Melt  and  STRENGTH. 
stir  the  solution,  and  place  in  a  refrigerator  for  at 
least  15  hours  at  a  temperature  between  5  and  10. 
degrees  C.  (40  to  50  degrees  F.)  Test  either  in  the 
refrigerator  or  immediately  after  removal.  The 
operator  uses  the  third  finger  of  the  left  hand  and 
measures  the  resistance  by  pressing  on  the  glue  jelly. 
Any  difference  between  different  samples  is  noted,  and 
the  samples  may  be  grouped  in  accordance  with  this 
resistance. 

In  the  Lipowitz  test  a  small  pointed  plunger  with 
a  funnel  at  its  upper  end  is  inserted  in  the  jelly.    The 
funnel  is  loaded  gradually  with  shot  until  the  load  THE  LIPOWITZ 
is  just  sufficient  to  force  the  plunger  entirely  through  TEST- 
the  jelly  from  its  top  surface  to  the  bottom  of  the 
cylinder.     The  weight  of  shot  necessary  to  effect  this 
gives  the  Lipowitz  number. 

An  apparatus  invented  by  Edmund  S.  Smith  is  on 
the  market  which  makes  jelly  tests  without  breaking 
the  surface  of  the  glue.  It  does  not  give  good  results 
on  extremely  high  or  low  grades.  It  is  rather  com- 
plicated, and  requires  frequent  cleaning  and  attention. 
It  consists  in  principle  of  a  thistle  tube,  over  which  is 


MODERN  GLUES  AND  GLUE  TESTING 


stretched  a  thin  sheet  of  rubber.  At  the  other  end  of 
the  tube  is  a  bulb  for  obtaining  air  pressure,  and  a 
sensitive  pressure  gauge  or  water  manometer.  The 
pressure  tube  is  also  filled  with  water.  The  observa- 
tion is  made  by  forcing  the  rubber  diaphragm  into 
THE  SMITH  the  glue  jelly  with  air  pressure  from  the  bulb.  The 
JELLY  TESTER,  measurement  of  jelly  strength  is  made  by  noting  the 
pressure  on  the  gauge  or  manometer,  and  the  amount 
that  the  diaphragm  is  forced  into  the  glue  is  measured 
or  controlled  by  a  reading  of  the  water  level  in  the 
pressure  tube.  The  jelly  strength  is  measured  on  the 
gauge  or  manometer.  The  apparatus  must  be  adjusted 
uniformly  on  the  different  samples  to  fee  tested,  and 
the  distortion  of  the  diaphragm  must  be  the  same  in 
each  test.  The  apparatus  is  covered  by  patent  No. 
911277. 

Jerome  Alexander  (Jour.  Soc.  Chem.  Ind.,  1906,  25, 
p.  160)  describes  a  device  "consisting  of  a  brass  cylin- 
drical vessel  supported  like  a  gas  tank  by  four  vertical 
rods,  against  which  it  slides  with  almost  frictionless 
roller  bearings.  This  brass  cup  is  allowed  to  rest  on  a 
truncated  cone  of  jelly  of  definite  size,  composition  and 
temperature.  Shot  is  gradually  poured  into  the  cup 
until  a  definite  expression  of  the  jelly  is  observed.  Be- 
neath the  cup  are  two  vertical  adjustable  brass  up- 
rights 3.5  c.  m.  high,  connected  with  an  electric  bell 
circuit.  When  the  cup  reaches  their  level  the  bell 
rings.  The  weight  of  the  brass  cup,  plus  the  weight 
of  the  shot,  gives  a  figure  which  expresses  the  jelly 
strength." 

After  thoroughly  testing  most  of  the  above 
methods,  as  well  as  numerous  other  ones,  an  apparatus 
was  adopted  at  the  Forest  Products  Laboratory  that 
is  described  in  the  appendix.  This  apparatus  was 
modified  from  one  in  use  in  the  glue  laboratory  of 
Armour  &  Co.,  Chicago.  (See  Appendix.) 

The  jelly  test,  together  with  viscosity,  are  the  most 
important  of  the  tests  made  on  glues,  and  all  other 
tests  must  be  considered  in  conjunction  with  them  if 
the  operator  is  to  form  a  true  conception  of  the  grade 
of  the  glue  sample.  Both  tests  must  always  be  made 
to  obtain  a  fair  comparison  between  an  unknown 


JELLY   STRENGTH  39 

sample  and  one  of  Peter  Cooper's  standard.     To  say 

that  a  glue  tests  1  Extra  means  that  its  jelly  strength 

and  its  viscosity  must  be  the  same  as  a  standard  sample 

of  Peter  Cooper's  1  Extra.     Obviously,  the  operator  GLUE  STANDARD 

must  secure  standards  of  known  strength  before  he  SAMPLEs  ARE 

can  rate  his  glues,  as  it  is  practically  impossible  to  de-  XEEDED- 

fine  a  method  of  test  and  an  apparatus  with  sufficient 

exactness  that  the  glue  may  be  rated  without  the  use 

of  standards  of  comparison.     Therefore  it  is  of  the 

utmost  importance  that  the  operator  secure  or  have  in 

his  possession  standards  of  known  value  before  he 

can  rate  and  value  the  unknown  sample.    Peter  Cooper 

standards  may  be  purchased  from  the  Peter  Cooper 

Glue  Company. 

In  making  jelly  strength  tests  it  is  well  to  re- 
member that  sulphates  in  the  glue  increase  the  jelly 
strength  (as  well  as  viscosity),  while  chlorides  and 
nitrates  diminish  it. 


CHAPTER  VIII. 

STRENGTH  OF  THE  GLUED  JOINT. 

EVERY  user  of  glue  in  wood  work  is  interested 
in  the  strength  of  the  glue.  Hence  numerous  ef- 
forts have  been  made  to  devise  tests  that  would 
measure  the  strength  of  the  glue  in  the  joint.  The 
literature  is  full  of  descriptions  of  tests  of  one  sort 
or  another,  and  quite  frequently  statements  are  found  JOINT 
to  the  effect  that  the  results  obtainable  are  variable  or  STRENGTH 
unreliable.  Many  thousands  of  tests  have  been  made  TESTS  MAY  BE 
at  the  Forest  Products  Laboratory,  Madison,  Wis.,  and  DECEPTIVE. 
as  a  result  of  these,  the  author  is  forced  to  admit  that 
most  of  them  do  not  measure  the  strength  of  the  glue, 
but  rather  are  a  measure  of  the  quality  of  workman- 
ship or  skill  of  the  operator  in  making  the  joint.  With 
the  utmost  skill  and  the  best  methods  of  workman- 
ship, it  is  possible  to  produce  joints  with  grades  1*4 
or  higher  that  will  always  break  the  wood.  Possibly 
the  grade  of  1%  may  be  the  dividing  point.  Dense 
maple,  chosen  because  of  its  great  shear  strength,  was 
used  in  these  tests.  Some  information  on  grades  below 
1%  may  be  obtained  by  strength  tests.  Usually  speci- 
mens glued  in  the  factories  or  by  the  average  carpenter 
fail  in  the  glued  joint — many  hundreds  of  such  have 
been  sent  in  for  testing.  But  the  same  glues  can  be 
made  to  give  a  joint  so  strong  that  wood  failures  result. 
The  best  joints  made  by  carpenters  and  workmen  have 
been  produced  with  grades  about  Peter  Cooper  No.  1. 
Glues  grading  higher  probably  set  too  fast,  and  since 
the  workman  does  not  often  produce  a  joint  100  per 
cent,  perfect,  those  grading  below  that  do  not  develop 
the  full  strength  of  the  wood. 

The  glue  chemist  should  have  a  rather  clear  un- 
derstanding of  the  fundamentals  of  testing  glue  joints, 
or  he  may  draw  erroneous  conclusions  from  his  results. 
He  is  possibly  more  liable  to  be  measuring  his  own 
ability  to  do  "stunts"  with  the  glue  rather  than 
measure  the  strength  of  the  glue.  In  any  case,  with 
grades  above  1%,  watch  yourself  closely.  The  strength 


42 


MODERN  GLUES  AND  GLUE   TESTING 


THE  SELECTION 
OF  WOODS  FOR 
GLUE  TESTS.! I 


test  has  been  very  useful  in  obtaining  data  on  the 
effect  of  various  operations,  such  as  time  of  pressure, 
etc.,  on  the  strength  of  the  glue  joint.  It  is  also  true 
that  a  good  strong  joint  cannot  be  obtained  with  a  glue 
that  lacks  adhesiveness. 

In  order  to  develop  as  nearly  as  possible  the  full 
strength  of  the  glue  it  is  necessary  to  use  wood  of 
good  gluing  qualities  and  of  high  shearing  properties. 
Not  all  species  meet  these  requirements.  The  following 
table,  based  on  tests  on  small  clear  specimens  of 
material,  gives  a  number  of  species  which  have  an 
average  unit  value  in  shear  parallel  to  the  grain  of 
over  2,400  pounds  per  square  inch  at  8  per  cent,  mois- 
ture, as  well  as  a  number  of  other  common  species  with 
shearing  strength  below  this  value. 

In  general  the  shearing  strength  of  wood  when  the 
surface  of  failure  is  tangential  is  about  8  per  cent, 
greater  than  when  the  surface  of  failure  is  radial.  This 

SHEARING   STRENGTH   OF  WOODS  AT  8   PER  CENT 
MOISTURE  WITH  SPECIFIC  GRAVITY  VALUES 


Specific  gravity 
oven  dry  based 
on  volume 
When 

When    oven- 
Species  green     dry 
Ash,  white  (forest  grown)     .52         .60 

Beech   54         .66 

Birch,  sweet 59         .70 

Cherry,  black. 47        .53 

Dogwood  (Flowering) 64         .80 

Gum,   red 44        .53 

Hickory,  big  shellbark 62 

Locust,  black 66         .71 

Locust,  honey 60         .67 

Maple,   sugar 56         .66 

Oak,  Canyon  live 70         .84 

Oak,   Commercial   red 56         .67 

Oak,  Commercial  white 59         .71 

Persimmon  :...     .64         .78 

Walnut,   black 51         .56 

Yew,  western 60         .67 


Shear  parallel  to 

grain    surface  of 

failure 

Tan- 

Ra-     gen-  Aver- 

dial*    tialt  age 

2331    2021  2176 

2256    2397  2326 

2873    2811  2842 

1780    2294  2037 

2680  

1734         1900  1817 

2510         2536  2523 

2516         3391  2954 

2391         2514  2452 

2602         3030  2816 

2370         2628  2499 

1906         2263  2084 

2136         2466  2302 

2185    "     2671  242S 

1273         1552  1412 

2326         2861  2594 


*  By  radial  surface  of  failure  is  meant  a  plane  of  failure  per- 
pendicular to  the  growth  rings. 

tBy  tangential  surface  of  failure  is  meant  a  plane  of  failure 
parallel  or  tangent  to  the  growth  rings. 

IIFrom  paper  by  L.  J.  Markwardt,  Forest  Products  Labora- 
tory. 


STRENGTH    OF    THE    GLUED   JOINT 


43 


44 


MODERN  GLUES  AND  GLUE  TESTING 


SHEARING 
STRENGTH  OF 
WOOD. 


VARIATION   IN 
STRENGTH 
OF  WOOD. 


indicates  that  higher  values  would  be  secured  from  most 
species  by  makir.g  the  surface  of  failures  tangential,  but 
in  some  species  the  reverse  appears  to  be  true.  The 
radial  shearing  strength  would  be  influenced  to  a  con- 
siderable extent  by  any  season  checks  which  may  exist 
in  the  material,  and  consequently  any  material  contain- 
ing checks  should  be  eliminated. 

The  probable  variation  of  the  results  of  a  single 
test  from  the  average  of  the  species  is  less  for  shear 
than  for  some  of  the  other  important  mechanical  prop- 
erties. This  indicates  that  deviations  from  the  average 
values  given  in  the  table  would  be  smaller  for  shear 
than  for  the  other  properties.  In  general,  in  species 
having  a  shearing  strength  of  2,600  pounds  per  square 
inch  about  three-fourths  of  the  pieces,  without  selection, 
would  be  expected  to  give  unit  shear  values  above  2,400 
pounds.  The  proportion  of  individual  pieces  having  a 
shear  strength  greater  than  2,400  pounds  would,  of 
course,  be  larger  for  species  whose  average  shearing 
strength  is  above  2,600  pounds  per  square  inch. 

The  shearing  strength  of  wood,  like  the  other 
mechanical  properties,  is  closely  related  to  the  density 
or  dry  weight  of  the  material.  In  general  the  lighter 
species,  therefore,  are  inferior  to  the  denser  ones  in 
shearing  strength,  and,  likewise,  within  a  given  species 
the  heavier  pieces  would  normally  exceed  in  strength 
those  which  are  lacking  in  density.  The  selection  of 
material  on  a  density  basis  consequently  presents  a 
method  by  which  the  poorer  specimens  of  most  species 
may  be  eliminated.  In  species  having  an  average  shear- 
ing value  of  2,800  pounds  per  square  inch,  about  three- 
fourths  of  the  individual  pieces  5  per  cent,  below  the 
corresponding  average  density  would  be  expected  to 
give  unit  shear  values  of  2,400  pounds  or  over,  while 
about  half  the  pieces  at  10  per  cent,  below  the  average 
density  equal  or  exceed  the  latter  shearing  stress. 

The  moisture  content  of  the  wood  when  below  the 
fiber  saturation  point*  is  another  factor  which  influ- 

*The  fiber  saturation  point  is  that  point  at  which  no  water 
exists  in  the  pores  of  the  timber,  but  at  which  the  cell  walls  are 
still  saturated  with  moisture.  The  fiber  saturation  point  varies 
with  the  species.  The  ordinary  proportion  of  moisture,  based 
on  the  dry  weight  of  wood,  at  the  fiber  saturation  point,  is  from 
20  to  30  per  cent. 


STRENGTH    OF   THE   GLUED   JOINT 


45 


VARIATION  IN 
APPLICATION 
OF  GLUE  AND 
MANUFACTURE 
OF  JOINT. 


ences  the  strength,  the  strength  increasing  with  de- 
crease of  moisture.     In  general,  a  moisture  content  EFFECT  OF 
above  this  point  does  not  affect  the  strength.     The  MOISTURE  ON 
material  for  gluing  should,  therefore,  probably  be  at  STRENGTH. 
least  as  low  at  13  per  cent,  moisture. 

While  a  number  of  species  have  very  high  shearing 
values,  several  other  points  must  be  taken  into  con- 
sideration in  selecting  material  for  glue  tests,  such  as 
the  property  of  taking  glue,  and  availability.  Sugar 
maple  has  been  found  to  give  very  good  results,  is  easy 
to  procure,  and  when  straight  grained  and  free  from 
defects  is  recommended  as  a  shearing  material  for  glue 
tests.  Sweet  birch  would  likewise  be  expected  to  prove 
satisfactory  for  this  purpose. 

The  question  of  the  significance  of  joint  strength 
tests  made  on  grades  better  than   1%  has  already 
been  raised.     It  has  been  found  that  joints  made  at 
just  the  instant  the  glue  begins  to  chill  are  very  strong. 
It  is  almost  impossible  to  always  have  the  glue  film  of 
the  same  thickness  in  successive  test  pieces,  and  the 
thickness  of  the  film  very  markedly  affects  the  joint. 
Above  all  avoid  a  film  too  thin  (a  starved  joint).    A 
starved  joint  can  be  obtained  by  using  too  much  pres- 
sure.   It  will  be  obvious  that  before  the  operator  can 
feel  that  the  results  of  his  strength  tests  are  reliable  REQUIREMENTS 
he  must  know  all  the  essentials  of  producing  a  perfect  FOR  OBTAINING 
joint,  and  be  perfectly  certain  that  he  has  succeeded  MAXIMUM 
in  doing  so.    He  is  advised  to  do  considerable  experi-  STRENGTH. 
menting  with  joints  made  under  different  conditions 
before  relying  upon  his  results. 

This  more  properly  resolves  itself  into  a  discussion 
of  methods  of  testing.    It  is  of  course  possible  to  ob- 
tain   some    information    from    almost    any    sort    of 
strength  test  that  will  rupture  the  glued  joint.    Thus 
the  workman  may  try  to  split  the  joint  with  a  chisel. 
If  it  follows  the  glue,  either  he  has  a  poor  joint  or  the  IMPROPER 
glue  is  weak.     Such  tests  are  relatively  of  very  little  APPLICATION  v 
value,  as  even  low  grade  glues  may  not  split  along  the  OF  THE  LOAD. 
joint  if  a  soft  or  weak  wood  is  used.    With  very  hard, 
strong  woods  it  is  possible  to  obtain  an  idea  of  the 
strength,  but  not  in  terms  that  can  be  readily  ex- 
pressed.   Such  tests  should  be  carried  out  on  strong 


46 


MODERN  GLUES  AND  GLUE   TESTING 


APPLY   LOAD 
UNIFORMLY. 


THE   SPAN  DA  U 
TEST. 


woods,  as  maple  or  birch.    Even  oak  is  hardly  strong 
enough  in  shear  to  test  ordinary  grades  of  glue. 

When  the  attempt  is  made  to  measure  the  load 
necessary  to  rupture  either  the  wood  or  the  glued  joint, 
the  results  are  liable  to  be  so  variable  as  to  mean 
nothing  unless  properly  applied.  Any  test  that  does 
not  apply  the  load  uniformly  over  the  test  piece  is 
to  be  regarded  as  of  doubtful  value.  Such  tests  usually 
can  be  resolved  into  applying  the  load  on  the  joint  in 
shear,  in  tension,  in  cleavage  or  by  twisting.  Only  the 
first  two  should  be  considered  by  the  glue  tester.  In 
the  latter  two  the  load  is  concentrated  on  small  areas, 
which  give  way  and  allow  the  load  to  then  be  con- 
centrated on  adjacent  areas.  The  piece  can  never 
show  its  maximum  strength,  as  it  can  when  the  load 
is  applied  uniformly. 

This  is  a  test  proposed  by  Karmarsch  and  adopted 
by  the  Artillerie  Werkstatte,  Spandau.  It  has  been 
much  used  in  America.  Cement  testing  machines  are 
often  used,  or  sometimes  a  system  of  levers  is  devised 
that  works  well.  Samuel  Rideal  (Glue  and  Glue  Test- 
ing) reports  great  difficulty  in  obtaining  check  results, 
due  to  non-uniformity  in  the  wood,  and  in  the  surface 
of  the  wood  at  the  glued  joint ;  time  of  heating  the  glue 
and  temperature  of  gluing,  thickness  of  glue,  pressure 
used,  uneven  application  of  pressure,  presence  of 
lumps;  variation  in  the  moisture  in  the  air,  tempera- 
ture while  setting,  duration  of  time  between  gluing  and 
testing ;  temperature  while  testing ;  uneven  application 
of  load.  Truly  a  formidable  list  of  causes  for  varia- 
tion, and  obviously  requiring  skill  and  knowledge  of 
the  subject  to  secure  consistent  results. 

The  Spandau  test,  as  officially  adopted  in  Germany, 
consists  in  gluing  together  two  blocks  of  wood  with  a 
plain  butt  joint  with  the  grain  end  to  end.  The  blocks 
are  40  mm.  square  in  cross  section,  and  210  mm.  long. 
The  glue  stock  is  prepared  by  dissolving  250  grams 
of  glue  in  500  c.  c.  of  water.  The  blocks  having  been 
glued  together,  one  is  fixed  horizontally  to  a  table  in 
such  a  manner  that  the  joint  between  the  two  blocks 
overhangs  beyond  the  edge  of  the  table.  A  scale  pan 
is  attached  to  the  block  at  a  given  distance  beyond  the 


STRENGTH   OF   THE   GLUED   JOINT 


47 


edge  of  the  table  and  weights  are  added  until  the 
'joint  fractures. 

This  test  cannot  be  recommended  very  highly,  be- 
cause it  places  the  top  of  the  joint  at  a  maximum 
strain,  while  the  bottom  is  in  compression.  A  uni- 
formly applied  load  is  much  superior. 

A   test   adopted    by   the    British    Royal   Aircraft 
factory  in  their  specification  of  Nov.,   1916,  uses  a 
double  wedge  shaped  block  (See  Fig.  2).     It  is  made  BRITISH  BLOCK 
by  gluing  together  two  pieces  of  American  walnut.  AIRCRAFT  TEST. 


Glue  Joint 
FIG.  2 

The  glue  solution  is  prepared  according  to  the 
glue  manufacturer's  instructions.  The  test  joint  has 
dimensions  3  in.  by  1  in.,  and  is  required  to  support 
a  static  load  of  187  pounds  per  square  inch  in  direct 
tension.  The  test  is  made  at  122°  F.  at  normal 
humidity,  in  a  fully  saturated  atmosphere,  and  sub- 
merged in  water.  The  load  must  be  supported  for 
various  lengths  of  time  in  these  tests,  depending  upon 
the  grade  of  glue  desired. 

The  Aeronautical  Inspection  Directorate  (Eng- 
land) tests  a  sample  of  the  form  shown  in  Fig.  3. 

American  walnut  is  used  and  the  glued  surfaces 


Gluo  Joint 


FIG.  3 


48 


MODERN  GLUES  AND  GLUE  TESTING 


slightly  tooth-planed.     The  specimen  is  supported  at 
the  ends  in  a  testing  machine  and  the  load  applied  in 
ANOTHER  the  center.    Precautions  are  specified  for  the  tempera- 

BRITISH  TEST,  tures,  pressures  used  in  gluing,  preparation  and  appli- 
cation of  the  glue,  etc.,  that  insure  reasonably  uniform 
results.  The  fundamental  objection  is  that  the  load  is 
not  uniformly  applied  to  the  glued  joint.  Fairly  con- 
sistent results  may  be  obtained,  however. 

Of  the  numerous  methods  experimented  with  at  the 
Forest  Products  Laboratory,  Madison,  Wis.,  the  ten- 
sion test  and  the  shear  test  were  the  only  ones  that 
gave  reasonably  accurate  results.  The  tension  test 
was  discarded  because  it  does  not  represent  the  most 
common  practice  of  gluing  wood,  and  is  furthermore 
inconvenient  and  slow.  It  can,  in  one  form  or  another, 
however,  be  satisfactorily  used  to  determine  glue 
strength. 

Glue  Joints 


FIG.  4 


AVOID  THIS 
METHOD. 


A  test  specimen  as  shown  in  Fig.  4  has  been  widely 
used*,  but  was  discarded  at  the  laboratory.  This 
specimen  is  made  of  three  pieces  glued  in  the  form 
shown,  with  4  square  inches  in  each  joint.  The  speci- 
men is  placed  in  the  testing  machine  and  tested  in  com- 
pression. This  test  appeals  to  people  because  it  does 
not  require  a  tool  or  special  device  to  test  in  a  testing 


*See  Jerome  Alexander  (Jour.  Soc.  Chem.  Industry,  1906,  25, 
160). 


STRENGTH   OF   THE   GLUED   JOINT 


49 


machine.    It  is  not  recommended,  however.    It  is  men- 
tioned here  because  of  its  rather  widespread  use,  and 
the  temptation  to  use  it  in  the  absence  of  complete 
equipment.     The  objection  lies  in  the  fact  that  when 
the  load  is  applied,  the  two  outer  pieces  spread  apart 
at  the  bottom,  giving  a  failure  in  cleavage  instead  of  u.  s.  ARMY 
in  shear.     The  test  as  finally  adopted  at  the  Forest  AND  NAVY  TEST. 
Products  Laboratory  uses  a  specimen  as  in  Fig.  5.    The 


FIG.  5 


wood  is  prepared  conveniently  as  in  Fig.  6,  which  is 
self  explanatory.  It  is  necessary  to  use  a  shear  tool. 
A  drawing  of  this  is  shown  in  Fig.  7.  Fig.  8  shows  a 
specimen  under  test  in  the  testing  machine. 

A  complete  description  of  the  Forest  Products 
Laboratory  method  is  given  in  the  appendix.  A  modi- 
fication of  this  method  has  been  used  to  some  extent  by 
sawing  the  specimen  as  shown  in  Fig.  9. 

This  specimen  is  then  tested  in  compression  with- 
out the  use  of  a  shearing  tool.  The  author  cannot 
vouch  for  this  method,  as  he  has  never  used  it. 

A  rather  common  method  of  glue  testing  is  to  cut 
a  series  of  boards  as  shown  in  Fig.  10.    These  boards  A  SIMPLE  BUT 
are  glued  together  as  the  vertical  straight  lines  in-  INACCURATE 
dicate.    After  the  glue  has  set,  a  wedge  is  driven  in  METHOD. 
at  the  places  indicated  by  the  arrows.     The  claim  is 
made  that  a  good  grade  of  glue  should  always  hold 
the  pieces  together  so  firmly  that  the  glue  joint  does 
not  give  way,  but  that  the  wood  itself  will  split  or  be 


50 


MODERN  GLUES  AND  GLUE   TESTING 


Ghed  Joint 


Spec\mensl-~Firs't  Step 


METHOD  OF  PREPARING  SPECIMENS 

FOB. 

GLUE  STRENGTH  TESTS 

FIG.  6 


STRENGTH    OF   THE   GLUED   JOINT 


51 


ruptured.  This  method  is  guesswork  and  yields  no 
results  for  the  reason  that  no  matter  how  much  the 
strength  of  the  wood  may  vary,  the  test  does  not  in- 
dicate this  variation.  Furthermore,  the  result  cannot 
be  expressed  in  figures. 


Another  common  method  is  to  glue  up  two  pieces 
from  10  to  12  inches  in  length  and  of  suitable  width 
to  fit  into  a  bench  vise.  After  the  glue  has  dried,  the 
glued  boards  are  placed  into  the  vise  so  that  the 


52 


MODERN  GLUES  AND  GLUE  TESTING 


entire  joint  stands  out  from  three  to  four  inches.  The 
workman  strikes  the  joint  with  a  hammer,  and  it  is 
claimed  that  if  the  glue  joint  is  weaker  than  the  wood 
the  joint  will  break;  if  not,  the  wood  will  split.  The 
results  obtained  in  this  test  are  absolutely  worthless. 


FIG.  8 


Figure  11  shows  a  simple  scheme  that  will  likely 
appeal  to  some. 

The  heavy  straight  vertical  line  represents  a  wall 
or  post.  A  represents  a  heavy  hinge  being  fastened 
to  the  wall  and  beam  B.  C  represents  a  block,  the 
end  being  rounded  so  as  to  fit  part  way  into  the  "V" 
cut  opening  of  the  glued  test  piece  E.  D  represents 
the  platform  of  a  so-called  platform  scale.  The  beam 


STRENGTH    OF    THE    GLUED    JOINT 


53 


is  10  feet  long  by  4  inches  by  2  inches.  The  test  piece 
is  usually  10  inches  by  3  inches  by  %  mcn  each,  two 
pieces  glued  together  and  the  top  cut  out  either  "V"  ™ 
or  "U"  shaped.  C  is  placed  in  the  opening  ;  this  block, 
as  the  illustration  will  indicate,  being  a  little  larger 
than  the  slot  into  which  it  is  fitted.  The  weight  on  the 
end  of  the  beam  required  to  break  the  pieces  is  read 
and  recorded. 


N0  TEST 


FIG.  9 


A  simply  made  lap  joint  test  is  worthy  of  men- 
tion. 

Carefully  selected  pieces  of  a  hard  wood  are  used 
for  this  test.     The  moisture  content  is  determined.  THIS  is  A 
The  pieces  are  jointed  and  sized,  so  that  they  will  be  FAIRLY  GOOD 
exactly  8  inches  long  by  1  inch  by  1  inch.    The  thick- 
ness and  width  should  be  determined  with  a  micro- 
meter. The  pieces  are  then  lap-glued  as  per  illustration, 


HOME-MADE 
DEVICE. 


FIG.  10 


54 


MODERN  GLUES  AND  GLUE  TESTING 


and  we  now  have  a  glued  surface  of  exactly  one 
square  inch.  In  studying  Fig.  12  the  reader  will  ob- 
serve blocks  B.  They  are  glued  into  the  corners  of  the 
testing  machine,  one  being  2  inches,  the  other  1  inch 
thick.  Par.  represents  a  partition  or  wall  through 
which  the  plunger  P  passes.  P  is  a  stick  of  wood  one 
inch  square  of  convenient  length  to  which  T,  a  support 
for  the  weights,  W,  is  fastened. 


c 

V 

D 

FIG.  11 

The  glued  pieces  are  stored  in  a  dry  room  for 
from  three  to  four  weeks.  The  test  strips  are  next 
placed  in  the  testing  machine  upon  blocks  B.  Weights 
are  added  on  T  until  the  lap  breaks,  and  the  weights 
to  accomplish  this  are  recorded.  The  objection  to  this 
method  is  that  the  load  is  not  applied  uniformly  over 
the  glued  joint. 


Test  pieces. 


6X7X7  6X1X1 


FIG.  12 


STRENGTH    OF   THE   GLUED   JOINT 55 

The    difficulty    of    obtaining    satisfactory    results 
from  strength  tests  on  glued  wood  joints  has  inevit- 
ably led  investigators  to  try  other  schemes  for  test-  MISCELLANEOUS 
ing  strength.     The   .experience    of    the    Forest    Pro-  STRENGTH 
ducts  Laboratory  has  led  them  to  feel  that  schemes  TESTS- 
for  testing  the  strength  of  the  film,  or  of  some  por- 
ous material  such  as  plaster  or  earth  cemented  to- 
gether with  the  glue  may  have  merit. 

A  method  of  glue  testing  suggested  by  Karmarsh 
and  modified  by  Weidenbusch,  1859,  consists  in  break- 
ing small  rocks  of  plaster  of  paris  cast  in  molds  of  A  PLASTER 
uniform   size   and   saturated   with   glue   solutions   of  R°D  TEST. 
known  strength  and  dried  thoroughly.    They  are  then 
horizontally  supported  at  their  ends  and  loaded  in  the 
center,  the  weight  required  to  break  the  rod  being  the 
so-called  Karmarsh,  or  Weidenbusch,  figure  for  the  cor- 
responding glue  solution. 

Setterberg    (Schwed,    techmks    Tideskrift,    1898, 
XXVIII,  52)   soaks  strips  of  paper  in  the  glue  solu- 
tion.   The  excess  of  glue  is  removed  with  filter  paper,  THESE  TESTS 
the  strips  allowed  to  dry,  and  tested  in  a  paper  testing  WARRANT 
machine.  CONSIDERATION. 

Gill  (Jour.  Ind.  and  Eng.  Chem.,  Feb.,  1915,  p. 
103)  tried  the  tension  test,  gluing  blocks  together 
endwise.  He  also  tried  porcelain,  glass,  and  tiling.  He 
could  not  secure  uniform  results,  and  then  dipped 
filter  paper  in  the  glue  solution,  dried  and  tested.  His 
conclusions  are  as  follows :  "The  method  of  testing  glue 
by  measuring  the  strength  which  it  imparts  to  bib- 
ulous paper  is  dependable  and  gives  fairly  concordant 
results." 


CHAPTER  IX. 

PLYWOOD  STRENGTH  TEST.* 

A  HIGHLY  satisfactory  method  of  testing  glues  in 
veneer  panels  or  plywood  was  developed  at  the 
Forest  Products  Laboratory.     It  was  adapted 
from  the  English  A.  I.  D.  method.     An  experienced  TEST  SUITABLE 
operator  can  make  from  500  to  1,000  tests  a  day.    A  FOR  VENEER 
large  number  of  tests  on  each  glue  may  thus  be  made,  WORK. 
reducing  the  variables  due  to  a  small  number  of  tests. 
The  specimen  for  this  test  is  prepared  as  shown 
in  Fig.  13  and  the  test  is  made  by  placing  the  speci- 


i 
j 


FIG.    13 


men  in  the  grips  of  a  testing  machine  and  exerting  a 
pull  upon  it.  This  causes  the  joint  to  fail  either  in  the 
glue  or  the  wood,  or  both.  The  English  requirement 
is  that  the  glue  joint  in  the  plywood  must  show  a 
strength  of  at  least  150  pounds  per  square  inch  in  this 
test  to  be  acceptable.  On  the  basis  of  several  thousand 
tests  on  plywood  secured  from  various  American  manu- 
facturers it  appeared  that  a  minimum  average  of  150 
pounds  per  square  inch  may  also  be  safely  required  for 
American  plywood. 


*From  paper  prepared  by  Teesdale  and  Colgan,  Forest  Prod- 
ucts Laboratory. 


58 


MODERN  GLUES  AND  GLUE  TESTING 


Fig.  14  shows  the  style  of  grips  first  used,  as  recom- 
mended by  the  English  reports,  to  do  away  with  the 
free  pivot  motion  allowed  by  these  grips  a  special  jaw 
was  designed  as  shown  in  Fig.  15.  These  jaws  were  in- 


FIG.  14 


serted  in  the  Riehle  cement  tester  as  shown  in  Fig.  16. 
The  upper  jaw  is  hung  on  a  knife  edge,  since  it  is  a 
part  of  the  leverage  system  of  the  balance.  The  lower 
jaw  is  rigidly  fastened  except  for  the  vertical  motion  in 
oeprating  the  machine.  A  guide  attached  to  it  counter- 
acts the  tendency  of  the  upper  jaw  to  swing  in  the  di- 
rection of  opening  of  the  upper  saw  cut. 

When  adjusting  a  specimen  into  these  jaws  the  only 
additional  precaution  necessary  is  to  make  sure  that 


PLYWOOD   STRENGTH    TEST 


59 


it  is  centered  in  order  to  get  a  straight  pull.  This  is 
done  by  adjustable  thumb  screws  which  control  the 
position  of  the  grips. 

The  bucket  attached  to  the  lower  arm  at  the  left 
contains  small  lead  shot,  which  are  released  by  a  valve- 
like  mechanism  and  flow  into  the  pan  on  the  spring 
scale  placed  below.    The  load  is  applied  to  the  specimen  now  TEST  is 
in  the  holder  by  means  of  the  wheel  at  the  right.    As  MADE. 


FIG.  15 

the  load  is  applied,  the  shot  are  released  from  the  buck- 
et and  flow  into  the  pan  on  the  scale,  which  indicates 
the  actual  load  applied.  When  the  specimen  breaks  the 
flow  of  shot  is  automatically  stopped. 

The  difference  between  the  strength  values  shown 
in  the  shear  test  on  blocks  and  the  English  test  on 
plywood  is  due  to  several  reasons.  In  the  shear  blocks, 


60 


MODERN  GLUES  AND  GLUE   TESTING 


the  grain  of  the  two  pieces  glued  together  runs  in  the 
same  direction,  while  in  plywood  the  grain  of  the  plies- 
WHY  PLYWOOD    runs  m  opposite  directions.    Changes  in  moisture  con- 
STRENOTH  tent  due  to  the  drying  of  the  glue  in  the  joint  will, 

TESTS  GIVE         therefore  cause  stresses  in  the  joint  in  the  plywood  to 
LOW  VALUES.      a  very  much  greater  extent  than  the  shear  blocks,  be- 
cause the  shrinkage  of  wood  is  much  greater  across 
the  grain  than  along  the  grain.    Also  in  making  joints 


FIG.  16 


PLYWOOD   STRENGTH    TEST  61 

in  thick  material  greater  care  is  possible  in  the  prep- 
aration of  the  surface  and  the  application  of  the  glue 
than  in  plywood.  The  continued  flexing  of  plywood  in 
handling  also  may  have  some  weakening  effect  on  the 
glue. 

The  panels  to  be  tested  are  cut  into  specimens 
one  inch  by  three  and  one-fourth  inches ;  the  test  area 
being  restricted  to  one  square  inch  by  notches  cut  DETAILED 
through  one  face  and  the  core,  on  opposite  sides  of  the  DESORIPTION 
panel,  one  and  one-eighth  inches  from  each  end.  OF  PLYWOOD 

A  panel  should  preferably  be  three-ply  and  should  TESTS. 
not  have  a  core  which  exceeds  one-eighth  inch.  Thin- 
ner cores  are  preferable.  When  thick  panels  are  test- 
ed, it  is  sometimes  necessary  to  plane  them  down  to  a 
thickness  suitable  for  the  machine  before  testing  them. 
Panels  with  1/64-in.  plies  are  too  thin  to  test,  because 
it  is  practically  impossible  to  make  them  into  shear 
specimens  without  spoiling  them.  This  test  may  be 
used  to  test  the  quality  of  glue  or  of  workmanship  in 
veneer  panels.  It  may  also  be  used  to  test  the  water 
resistance  of  glups  by  placing  the  test  specimens  in 
water  or  under  humid  conditions  before  being  tested. 


63 


CHAPTER  X. 

SPECIFICATIONS. 

readers  inexperienced  in  glue  testing  may 
have  gained  the  impression  that  the  methods  of 
-*-  test  are  unreliable  and  of  little  value.  This  is 
by  no  means  the  case.  It  is  true  that  testing 
methods  are  arbitrary,  and  that  they  cannot  in 
general  be  expressed  in  terms  of  numerical  values  with 
sufficient  exactness  to  write  a  specification.  It  was  THE  ARMY  AND 
for  this  reason  that  in  the  work  of  the  Forest  Products  NAVY  GLUE 
Laboratory,  all  thought  of  attempting  to  prepare  a  SPECIFICATIONS. 
specification  without  the  use  of  a  standard  sample  was 
abandoned.  The  specification  as  evolved  makes  use  of 
a  standard  sample  which  was  selected  as  being  satis- 
factory for  the  purpose,  and  of  a  grade  not  difficult 
to  obtain.  The  specification  then  requires  the  manu- 
facturer to  furnish  glue  at  least  equal  to  the  standard 
sample  in  jelly  strength,  viscosity,  grease,  foam  and 
odor.  After  two  years  of  use,  covering  purchases  of 
over  a  million  pounds  of  glue  for  both  the  army  and  the 
navy,  it  can  be  said  that  the  specification  was  very 
satisfactory,  both  to  the  manufacturer,  the  consumer 
and  the  specification  department.  Hence  it  can  be 
recommended  unqualifiedly  to  any  purchaser  of  glue 
in  quantities  sufficient  to  warrant  the  expense  of 
making  tests.  It  would  only  be  necessary  for  the  buy- 
er to  determine  upon  a  standard  sample  of  the  quality 
he  desires,  and  set  aside  a  quantity,  say  50  or  100  Ibs., 
to  be  used  as  a  standard  sample.  The  specification  as 
given  would  apply  in  all  respects  except  "adhesive- 
ness," where  the  required  strength  values  would  change 
with  the  grade  of  the  standard  sample.  In  these  speci- 
fications the  standard  is  about  the  equivalent  of  Peter 
Cooper's  grade  1. 

1.  This  specification  covers  the  requirements  of 
the  Bureau  of  Aircraft  Production  for  all  hide  glue 
used  in  the  construction  of  propellers  and  for  splices 
of  airplane  structural  members. 


64 


MODERN  GLUES.  AND  GLUE  TESTING 


SPECIFICATIONS 
FOR  AIRPLANE 
USE- 


STRENGTH 
TEST,   U.   8. 
ARMY. 


MODE  OF 
PROCEDURE. 


2.  The  glue  must  be  a  high  grade  hide  glue,  sweet 
and  free  from  any  deleterious  substances. 

3.  The  glue  shall  be  tested  by  comparison  with 
a  standard  sample  for  jelly  strength,  viscosity,  grease, 
foam  and  odor.    The  standard  sample  may  be  obtained 
from  the  Director,  Forest  Products  Laboratory,  Madi- 
son, Wis. 

4.  The  following  tests  shall  be  made  by  a  Bu- 
reau of  Aircraft  Production  representative  before  cer- 
tifying or  accepting  any  hide  glue  for  use  in  aircraft 
construction. 

5.  The  test  for  adhesiveness  shall  be    made  on  4 
test  specimens  of  the  form  and  dimensions  shown  in 
Fig.  5,  page  49.     The  test  specimens  shall  be  made 
of  maple  having  a  shearing  strength  of  at  least  2,400 
pounds  per  square  inch.    This  will  require  wood  hav- 
ing a  dry  weight  of  about  50  pounds  or  more  per  cubic 
foot,  and  a  moisture  content  of  from  8  to  12  per- 
cent. 

6.  The  glue  shall  be  mixed  with  water  in  four 
different  proportions  by  weight,  and  test  specimens 
shall  be  prepared  using  the  glue  at  each  of  these  four 
dilutions.    Unless  otherwise  specified,  the  proportions 
used  shall  be  as  follows: 


Water  1 

Glue  ...  1 


n. 


III. 


IV. 

2-% 


The  glue  shall  be  added  to  the  water  at  room  tem- 
perature, stirred  thoroughly,  and  allowed  to  stand  for 
at  least  two  hours.  It  shall  then  be  melted  in  a  water 
bath,  at  140  deg.  Fahr.  (60  deg.  C.)  and  applied  to 
the  wood  surfaces  which  are  to  be  placed  in  contact. 
These  surfaces  shall  fit  perfectly  together,  and  the 
wood  shall  be  at  room  temperature.  After  gluing,  the 
test  blocks  shall  be  held  under  a  moderate  and  uniform 
pressure  for  15  to  24  hours.  At  the  end  of  this  time 
they  shall  be  released  from  pressure  without  subjecting 
them  to  shock,  and  allowed  to  stand  for  6  days  addi- 
tional. The  test  specimens  shall  be  finished  so  that 
when  they  are  ready  for  testing  they  shall  have  a 
glued  joint  two  inches  square,  and  conform  to  Fig.  5. 
The  specimens  shall  be  tested  to  destruction  in  a  test- 


SPECIFICATIONS 65 

ing  machine  approved  by  the  Inspection  Department. 
No  test  specimen  shall  fail  under  a  load  of  less  than 
2,200  pounds  per  square  inch,  and  the  average  shearing 
strength  shall  be  at  least  2,400  pounds  per  square  inch. 
Specimens  which  fail  under  a  load  of  less  than  2,400 
pounds  per  square  inch  will,  if  the  failure  occurs  en- 
tirely in  the  wood,  be  excluded  in  calculating  the  aver- 
age shearing  strength  and  the  permissible  minimum. 
The  glue  mixed  with  water  in  at  least  one  of  the  four 
proportions  as  above  shall  comply  with  this  strength 
requirement.  The  dilution  at  which  the  greatest 
strength  is  indicated  will  be  recommended  for  use. 

7.  The  jelly  strength  shall  be  determined  upon  JELLY 

a  mixture  containing  12  parts  of  water  to  1  part  of  STRENGTH. 
glue.  The  glue  shall  be  soaked,  melted  and  poured 
immediately  into  a  vessel  of  standard  size  and  shape. 
It  shall  then  be  allowed  to  stand  for  at  least  15  hours 
in  a  refrigerator  at  a  temperature  of  from  40  to  50 
deg.  Fahr.  (5  to  10  deg.  C.).  The  relative  strengths 
of  the  standard  sample  and  the  glue  under  test  will 
be  determined  in  the  refrigerator,  or  immediately  after 
removal  therefrom,  by  pressure  with  the  fingers  or 
with  some  suitable  apparatus  approved  by  the  Inspec- 
tion Department. 

8.  The  viscosity  shall  be  determined  in  an  Eng-  VISCOSITY. 
ler  Viscosimeter  upon  a  sample  containing  1  weight 

of  glue  to  5  weights  of  water.  The  sample  shall  be 
strained  and  the  viscosity  shall  be  determined  within 
5  minutes  after  having  been  melted.  The  viscosity 
shall  be  expressed  in  terms  of  the  number  of  seconds  re- 
quired for  200  cubic  centimeters  of  the  glue  solution, 
at  a  temperature  of  60  deg.  C.,  to  pass  through  the  stan- 
dard orifice  of  the  viscosimeter. 

9.  The  relative  amount  of  grease  present  shall  be  GREASE. 
determined  by  mixing  a  dye  with  some  of  the  glue 
remaining  from  the  viscosity  test,  painting  the  mixture 

on  unsized  white  paper,  and  observing  the  appearance. 

10.  The  test  for  foam  shall  be  made  on  the  sample  FOAM. 
used  in  the  viscosimeter.     The  sample,  after  heating 

to  140  deg.  Fahr.  (60  deg.  C.),  shall  be  beaten  for  one 
minute  with  a  power  egg  beater,  or  similar  instrument, 


66 


MODERN   GLUES  AND  GLUE   TESTING 


INSPECTION. 


PRELIMINARY 
SAMPLE. 


and  allowed  to  stand  one  minute  or  until  the  foam  can 
be  measured. 

11.  The  odor  of  the  glue,  when  in  hot  solution, 
must  be  sweet  and  must  remain  sweet  for  48  hours; 
that  is,  free  from  any  suggestion  of  deteriorating  ani- 
mal matter. 

12.  The  inspector  shall  have  free  access  to  all 
parts  of  the  plant  where  this  glue  is  being  manufac- 
tured, and  shall  be  afforded  every  facility  to  satisfy 
himself  that  the  glue  is  in  accordance  with  this  speci- 
fication. 

13.  The  tests  shall  be  made  on  a  sample  from  each 
lot  of  glue.    The  manufacturer  of  hide  glue,  when  he 
has  accumulated  not  less  than  30,000  pounds  which  he 
considers  to  be  in  compliance  with  the  specification, 
will  make  up  a  sample  which  shall  be  representative  of 
the  whole  30,000  pounds,  grind  it,  if  it  is  not  already 
in  the  ground  condition,  and  send  at  least  a  2-pound 
sample  of  it  to  the  Senior  Inspector,  Bureau  of  Air- 
craft Production,  Forest  Products  Laboratory,  Madi- 
son, Wis.,  or  to  a  laboratory  designated  by  the  Inspec- 
tion Department,  Bureau  of  Aircraft  Production.     It 
must  be  plainly  marked  "Preliminary  Sample,"  and  it 
must  be  accompanied  by  a  written  statement  as  to 
the  amount  of  the  glue  represented  by  the  same  and  in- 
structions concerning  the  method  of  using  this  glue 
which  the  manufacturer  ordinarily  furnishes  the  user. 
He  shall  notify  the  Raw  Materials  Department  and  the 
Inspection  Department  at  Washington,  D.  C.,  when  the 
sample  is  forwarded. 

14.  This  sample  will  be  tested  by  Bureau  of  Air- 
craft Production  inspectors,  and  the  results  of  these 
tests  will  be  sent  to  the  manufacturer  as  soon  as  pos- 
sible. 

15.  If  the  preliminary  sample  passes  all  tests, 
the  manufacturer  may  proceed  to  mix  thoroughly  all 
the  glue  represented  by  the  sample.    He  will  advise  the 
inspectors  at  the  laboratory  on  what  date  it  will  be 
ready  for  final  mixing,  inspection  and  barreling.    As 
near  that  date  as  possible,  an  inspector  will  visit  the 
glue  factory.     In  his  presence,  the  glue  will  be  given 


SPECIFICATIONS 67 

such  final  mixing  as  he  deems  necessary.  It  will  also 
be  packed  in  tight  drums  or  barrels  in  his  presence; 
and,  at  the  same  time,  he  will  take  a  sample  which  will 
be  known  as  the  official  sample.  The  inspector  will  METHOD  OF 
forward  this  sample  to  the  Forest  Products  Labora-  SEALINO- 
tory,  or  to  a  laboratory  designated  by  the  Inspection 
Department,  for  analysis.  The  results  of  this  analysis 
will  determine  whether  or  not  the  hide  glue  can  be 
certified.  After  the  glue  has  been  placed  in  barrels, 
the  inspector  will  witness  the  "heading"  of  the  filled 
barrels,  and  will  seal  both  ends  of  every  inspected  bar- 
rel with  serially  numbered  labels  provided  for  the  pur- 
pose. Each  barrel  shall  also  be  marked  with  the  name 
of  the  glue. 

Note — The  submitting  of  the  preliminary  sample 
is  not  required  and  may  be  omitted  if  so  desired  by 
the  manufacturer. 

16.  The  manufacturer  will  then  put  the  inspected 
barrels  in  a  place  which  is  dry,  sheltered  and  suitable 
for  storage.     Glue  which   is  otherwise  satisfactory, 
will  be  rejected  if  proper  storage  facilities  are  not  pro- 
vided for  it. 

17.  If  the  official  sample  proves  to  be  in  compli- 
ance with  the  specification,  the  manufacturer  will  be 
notified  that  the  lot  of  glue     covered  by  the  official 
sample  has  been  certified.     Certified  hide  glue  is  the 
only  hide  glue  which  aircraft  manufacturers  will  be 
permitted  to  use.     Hide  glue  which  does  not  comply 
in  every  respect  with  this  specification  will  not  be 
certified,  and  its  use  will  not  be  permitted  on  govern- 
ment aircraft  contracts.     If  an  inspected  glue  fails 
to  be  certified,  the  manufacturer  will  be  required  to 
remove  the  inspection  labels. 

18.  The  glue  manufacturer  must  report  to  the  Raw 
Materials   Department,   Bureau  of  Aircraft  Produc- 
tion, and  to  the  Senior  Inspector,  Forest  Products  Lab- 
oratory, Madison,  Wis.,  every  sale  of  certified  hide 
glue.    The  reports  must  be  in  duplicate  and  they  should 
include  the  amount  of  glue,  the  number  of  the  label 
of  every  barrel  shipped,  the  name  and  address  of  the 
consignee,  and  the  date  of  shipment  (or  sale). 


68 


MODERN  GLUES  AND  GLUE  TESTING 


SPECIFICATIONS 
FOR  HANDLING 
HIDE  GLUE. 


GLUE    MUST 
BE     SOAKED 
AT   LEAST  TWO 
HOURS. 


NO  GLUE 
HEATED  LONGER 
THAN  8  HOURS 
CAN  BE   USED. 


19.  No  glue  which  has  been  rejected  shall  be  of- 
fered to  any  department  of  the  Bureau  of  Aircraft 
Production  or  to  any  aircraft  contractor  to  the  gov- 
ernment without  a  full  statement  of  the  cause  of  re- 
jection. 

1.  This  specification   is  drawn  to  cover  the  re- 
quirements of  the  Bureau  of  Aircraft  Production  for 
the  handling  and  testing  of  hide  glue  at  airplane  and 
propeller  factories. 

2.  All  the  animal  glue  used  in  the  construction 
of  propellers  and  for  splices  of  airplane  structural 
members  shall  be  hide  glue  certified  in  accordance  with 
Specification  No.  14,000-B. 

3.  Soaking. — The  glue  and  pure  cold  water  must 
be  weighed  out  separately,  and  according  to  the  pro- 
portions recommended  for  the  particular  glue  by  the 
Senior    Inspector,    Bureau    of    Aircraft    Production, 
Forest  Products   Laboratory:     They  should  then   be 
mixed,  thoroughly  stirred,  and  allowed  to  stand  in 
a  cold  place  in   a   covered  vessel   until   the  glue  is 
thoroughly  soaked  and  softened.     The  mixture  must 
stand  at  least  two  hours. 

4.  Melting. — After  the  glue  has  been  sufficiently 
soaked,  the  water-glue  mixture  shall  be  melted  on  a 
water  bath  or  in  a  carefully  regulated  electric  heater. 
The  glue  solution  must  never  be  permitted  to  rise  to 
a  temperature  exceeding  150  deg.  Fahr.     About  140 
deg.   Fahr.  provides  an  excellent  working  tempera- 
ture. 

5.  Heating. — Glue    shall    not    be    heated    for    a 
greater  length  of  time  than  is  absolutely  necessary. 
Glue  which  has  been  heated  for  8  hours  or  longer  must 
not  be  used.    All  the  glue  which  has  been  heated  at  any 
time  on  any  day  shall  be  rejected  at  the  close  of  that 
day  and  must  not  be  used  on  any  succeeding  day.     In 
order  to  prevent  the  loss  of  moisture,  the  glue  pot  shall 
be  kept  covered  when  not  in  actual  and  continuous 
use.    Any  skin  or  scum  which  forms  on  the  surface  of 
the  glue  shall  be  removed. 

6.  Application. — The  glue  shall  be  applied  to  the 
wood  in  a  room  which  is  free  from  draughts  and  as 


SPECIFICATIONS 69 

warm  and  humid  as  healthful  working  conditions  al- 
low. 

7.  Wood. — The  wood  shall  be  uniformly  dry  and 
at  least  as  warm  as  the  air  in  the  glue  room.     High 
temperatures  and  prolonged  heating  of  the  wood  should 
be  avoided  in  order  to  prevent  distorting  the  surface. 
The  wood  surfaces  shall  "fit"  perfectly  and  they  shall 
be  clean. 

8.  Spreading. — The  glue  shall  be  applied  to  both  APPLY  GLUE 
surfaces  of  the  joint,  and  shall  be  spread  freely  and  as  TO  BOTH 
rapidly  as  is  consistent  with  good  workmanship.  SURFACES. 

9.  Pressing. — The  clamp  pressure  or  other  pres- 
sure shall  be  applied  quickly  in  order  to  prevent  the 
glue  from  jellying  or  setting.    A  sufficient  number  of 
clamps  should  be  used  to  insure  that  the  wood  is  in 
close  contact  at  all  points,  and  that  the  pressure  is 
evenly  distributed. 

10.  Sanitation. — Only  enough  glue  shall  be  mixed 
at  any  one  time  for  one  day's  work.     The  glue  pots, 
brushes,  etc.,  shall  be  cleaned  out  each  night  with  boil- 
ing water  and  all  the  glue  left  over  after  the  day's 
work  shall  be  discarded.     The  brushes  will  remain 
sweet  if  left  over  night  in  a  solution  of  carbolic  acid. 

11.  A  glue  test  specimen  shall  be  made  of  1-inch  TEST 
boards  of  sufficient  size  to  furnish  ten  test  specimens  SPECIMEN. 
conforming  to  dimensions  specified  in  Fig.  5,  page  49. 

The  boards  shall  be  representative  of  the  wood  on 
which  the  glue  is  to  be  used.  The  specimen  shall  be 
made  up  under  the  average  conditions  prevailing  in  the 
glue  room.  The  gluing  shall  represent  actual  practice 
and  no  special  precautions  other  than  those  ordinarily 
taken  shall  be  employed  in  preparing  uie  glue  or  wood. 
The  gluing  shall  be  performed  by  the  employes  of 
the  airplane  factory  accustomed  to  this  kind  of  work.  TESTS  MUST 
No  protective  coating  of  any  kind  shall  be  applied  to  BE  MADE. 
the  wood  surfaces  or  to  the  finished  specimen.  The 
specimen  shall  be  held  in  the  clamps  for  15  to  24  hours. 
After  being  removed  from  the  clamps  it  shall  stand 
for  6  additional  days  in  a  warm,  dry  place.  The  speci- 
men shall  be  cut  into  ten  shear  blocks  which  conform 
to  the  dimensions  shown  in  Fig.  5,  page  49. 


70 


MODERN  GLUES  AND  GLUE  TESTING 


INSPECTION*. 


12.  The  following  test  shall  be  made  to  deter- 
mine the  strength  of  the  glued  joint.     Ten  of  the 
shear  blocks  shall  be  tested  in  a  shearing  machine 
immediately  after  sawing,   and  the  strength  of  the 
glue  in  shear  shall  not  be  less  than  that  of  the  wood. 

13.  The  required  strength  must  be  obtained  from 
80  per  cent,  of  the  specimens  tested. 

14.  Test  blocks  may  be  sent  to  the  Senior  In- 
spector, Bureau  of  Aircraft  Production,  Forest  Pro- 
ducts Laboratory,  Madison,  Wisconsin,  for  this  test. 
When  blocks  are  forwarded  for  this  test,  they  should 
be  plainly  and  clearly  marked  and  should  be  accom- 
panied by  Bureau  of  Aircraft  Production  I.  R.  Form 
No.  68  (Request  for  Glue  Tests). 

15.  The  inspector  of  the  Bureau  of  Aircraft  Pro- 
duction shall  have  free  access  to  all  parts  of  the  plant 
of  the  manufacturer  where  this  work  is  being  carried 
on,  and  shall  be  afforded  every  reasonable  facility  to 
satisfy  himself  that  the  work  is  in  accordance  with 
this  specification.    Tests  shall  be  made  under  the  super- 
vision of  a  representative  of  the  Bureau  of  Aircraft 
Production. 


CHAPTER  XI. 

RESULTS  OF  TESTS  ON  MISCELLANEOUS  GLUES. 

TESTS  in  accordance  with  the  methods  outlined 
in  the  foregoing  specifications  on  about  30  samples 
of  animal  glues  obtained  through  miscellaneous 
sources  were  made.     The  results  of  these  tests  are  of  T 
considerable  interest,  both  as  a  guide  to  the  operator  °£  J^HREE 
and  to  the  prospective  purchaser  of  glues.    The  results  L^BORATORIES 
are  given  in  Tables  1  to  9.     Some  of  these  samples 
were  sent  by  Laboratory  F  to  two  glue  manufacturers, 
termed  Lab.  A  and  Lab.  N,  where  the  tests  were  made 
by  their  own  methods.    The  comparisons  obtained  are 
very  interesting. 

Table  1  gives  a  description  of  the  samples  tested. 

The  results  of  the  viscosity  tests  are  given  in  Table 
2.    Since  a  different  type  of  viscosimeter,  and  probably 
a  different  volume  of  glue  solution  was  used  by  each  VISCOSITY 
of  the  three  laboratories,  the  results  cannot  be  directly  TSSTS. 
compared.     This  emphasizes  the  need  for  a  standard 
apparatus  and  method  of  determining  viscosities. 

In  Table  3  the  glues  are  arranged  in  order  of  their 
relative  jelly  strength.     This   arrangement  shows  n 
general  agreement  between  the  three  laboratories  as  JELLY 
to  which  are  the  strong  glues  and  which  the  weak. 

From  the  results  of  the  various  comparative  tests 
described  above,  it  might  be  presumed  that  these  tests 
are  of  little  value,  and  might  as  well  be  discarded.    This 
is  not  the  case,  however,  for  while  it  is  true  that  the 
results  from  different  laboratories  cannot  be  directly 
compared,  because  the  methods  of  test  are  different  and  THE  RESULTS 
because  of  the  personal  equations,  at  any  one  labora-  CANNOT  BE 
tory  the  value  of  a  glue  can  be  pretty  closely  approxi-  COMPARED 
mated  by  the  use  of  these  tests,  because  they  are  made  DIRECTLY. 
in  the  same  way  each  time.    The  results  above  quoted, 
however,  show,  very  emphatically,  the  need  for  a  stan- 
dard system  of  testing  to  be  followed  by  all  glue  lab- 
oratories. 


72 


MODERN  GLUES  AND  GLUE  TESTING 


The  reaction  of  the  various  glues  to  litmus  is  shown 
in  Table  4.  It  seems  strange  that  there  should  be  such 
a  disagreement  among  the  three  laboratories  as  to 
whether  the  glues  were  acid,  alkaline  or  neutral.  In 
most  cases,  of  course,  the  reaction  was  very  slight  in 
either  direction,  and  the  difference  must  be  due  either 


TABLE  1.—  DATA  ON  GLUE  SAMPLES. 


Kind  (Information  Price* 

Sample         from   manufac-  quoted 

No.  turer.)  per  Ib. 

1....     ....Animal. 


2  

Animal. 

J 

3  

Blend  of  fish  and 

46c 

animal. 

1 

4  

Animal. 

60c 

5  

F  i  r  s  t    run  pure 

51c 

hide  glue. 

7  
8  

Vegetable  glue. 

9  

V  e  r  y  high-grade 

glue. 

10  

Hide  glue. 

11..... 

Hide  glue. 

12  

Hide  glue. 

13.... 



14  

15.... 

Thin      cut      clear 

60c 

flake  glue. 

16 

Extra   clear   flake 

45c 

17.... 

glue. 
Medium  cut  clear 

50c 

flake  glue. 

18 

Highest      testing. 

19.... 

65c 

20.... 

Pure    rabbit    skin 

glue. 

21.... 

Exceptional  water 

55c 

taking  qualities. 

Less 

Freight 

22.... 

23 

24.... 

25.... 

26.... 



27 

....Pure  hide  elue. 

50c 

Remarks. 

Recommended  by  the 
manufacturer  for  hard- 
wood. 

Recommended  for  soft- 
woods. 

A  special  fish  blend  joint 
glue. 


Prepared  paste. 
Probably     a     casein 
product. 


From  lab.  stock.     Prob- 
ably foreign  glue. 


Contains  a  large  amount 
of  mineral  matter. 


28 High-test  glue. 

"June,  1917. 


RESULTS  OF  TESTS  ON  MISCELLANEOUS  GLUES 73 

to  the  difference  in  judgment  of  the  men  who  made 
the  tests,  or  to  a  difference  in  litmus  paper. 

Laboratories  A  and  N  did  not  report  upon  this  KEEPING 
test.    From  Table  5  it  is  apparent  that  practically  all  QUALITIES. 
the  glues  would  have  passed  a  test  requiring  that  they 
stand  48  hours  without  showing  signs  of  deterior- 
ation. 

Table  6  shows  typical  results  selected  at  random 
from  glues  tested  by  W.  L.  Jones,  B.  A.  P.  inspector  TYPICAL 
stationed   at   the    Forest    Products    Laboratory,    the  RESULTS 
methods  being  those  described  in  the  appendix.     The  OBTAINED  BY 
table  is  arranged  in  order  of  increasing  viscosities,  USE  OP  ARMY 
and  is  given  here  as  it  may  be  useful  to  the  operator  METHODS. 
attempting  to  use  the  proposed  methods. 

TABLE  2— RESULTS  OF  VISCOSITY  TESTS. 


Glue 
No. 

1  

Lab.F 
Seconds 

..   173.9 

Viscosity 
Lab.  A 
Seconds 

52.0 
50.0 
51.0 
50.0 
53.0 
58.8 
50.6 
55.5 
54.0 
44.0 
52.0 
55.5 
54.0 
55.0 
51.0 

5l'.5 
56.5 
50.5 

48.0 
49.6 
53.4 
42.0 
52.0 
58.6 

Ratio  to  Viscosity  of  Water 
Lab.N    Lab.F*  Lab.  Af    Lab.  NJ 
Seconds 

23.00           3.30           1.24           1.53 
21.00           2.69           1.19           1.40 
20.75           2.82           1.21           1.38 
20.75           2.65           1.19           1.38 
20.5             4.18           1.26           1.37 
25.00           5.48           1.40           1.67 
22.5             3.04           1.20           1.50 
24.25           4.39           1.32           1.62 
23.00           3.76           1.29           1.53 
18.25           1.62           1.05           1.22 
24.00           3.11           1.24           1.60 
25.00           4.70           1.32           1.67 
23.00           3.43           1.29           1.53 
24.00           4.03           1.31           1.60 
21.5              1.21           1.43 
27.5            4.98            1.83 
22.00           2.56           1.23           1.47 
26.25           4.14           1.34           1.75 
22.25           2.73           1.20           1.48 
20.75           2.34           1.14           1.38 
21.25           2.56           1.18           1.42 
25.00           3.62           1.27           1.67 
15.75           1.40          1.00           1.05 
23.25                            1.24           1.55 
27.00           4.90           1.39           1.80 

2  
3 

141.6 
148  4 

4  
5 

139.2 
219.7 

9  

288.5 

10  
11  

160.0 
231.0 

12  
13 

197.5 
850 

14  
15  
16  

163.8 
247.2 
180.3 

17 

212.0 

18 

19  
20  
21  
22  
23  

...   261.8 
134.8 
217.6 
143.6 
123.4 

24  
25 

134.8 
190.1 

26  
27.....  

28  

73.5 

".'.  257.7 

*Compared  with  the  viscosity  of  water  at  20°  C.,  which  is 
52.6  seconds  in  this  instrument.  (Engler.) 

fConipared  with  the  viscosity  of  water  at  60°  C.,  which  is 
about  42  seconds  in  this  instrument. 

^Compared  with  the  viscosity  of  water  at  20°  C.,  which  is 
15  seconds  in  this  instrument. 


74 


MODERN  GLUES  AND  GLUE  TESTING 


No.  Lab.  A' 

1 69 

2 64 

3 61 


TABLE  3— RESULTS  OF  JELL  TESTS 


4 

5 

9 

10 

11 

12 


65 
67 
73 
67 
71 
67 


13 Too    low 


14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 


26 Too 

27 70 

28 72 


Lab.  N* 
140 
120 

90 
110 

66 
166 
136 
152 
142 

50 

86 
164 
132 
146 
148 
144 
142 
134 
118 
136 

76 
138 

40 
154 


Lab.  Ff 

4 
5 
4 
3 
1 
3 
1 


NOTE— In  Laboratory!  tests, 
the  glues  were  classified  into 
groups  according  to  their 
strength  by  finger  test  method 
as  follows,  group  1  being  the 
strongest: 

Group  1— Nos.  9,  11,  28. 

Group  2— Nos.  23,  15,  19,  18, 
17,  21. 

Group  3— Nos.  15,  5,  12,  10,  1, 
27,  20. 

Group  4 — Nos.  14,  2,  25,  24,  4, 
22. 

Group  5 — No.  3. 

Group  6 — No.  13. 

Group  7— No.  26. 


156 

"These  values  represent  numerical  figures  obtained  with  the 
instruments  in  use  at  these  laboratories. 
tBy  finger  test  method. 


TABLE  4- 
No.  Lab.  F 

1 Slight   acid 

2 Slight   acid 

3 Very  slight 

4 Slight  acid 

5 Very  slight 

9 Slight  acid 

10 Slight   acid 

11 Acid 

12 Neutral 

13 Slight  acid 

14 Neutral 

15 Neutral 

16 Neutral 

17 Neutral 

18 

19 Neutral 

20 Acid 

21 Neutral 

22 Neutral 

23 Acid 

24 Neutral 

25 Neutral 

26 Neutral 

27 

28 Neutral 


acid 
acid 


REACTION  TO 
Lab. 
Alkaline 
Alkaline 
Alkaline 
Alkaline 
Alkaline 
Acid 
Alkaline 
Acid 
Alkaline 
Acid 
Alkaline 
Alkaline 
Alkaline 
Alkaline 
Alkaline 

Acid 

Alkaline 

Alkaline 

Acid 

Alkaline 

Alkaline 

Alkaline 

Acid 

Alkaline 


LITMUS. 

A  Lab.  N 

Very  slight  acid 

Very  slight   acid 

Very  slight  acid 

Neutral 

Very   slight   acid 

Very   slight   acid 

Very   slight   acid 

Very   slight  acid 

Neutral 

Fairly  much  acid 

Neutral 

Neutral 

Neutral 

Neutral 

Very   slight   acid 

Neutral 

Fairly  much  acid 

Neutral 

Very   slight   acid 

Slight  acid 

Neutral 

Neutral 

Neutral 

Slight  acid 

Neutral 


RESULTS  OF  TESTS  ON   MISCELLANEOUS  GLUES 


75 


A  very  interesting  series  of  results  is  published 
by  Linder  &  Frost  (Proc.  Am.  Soc.  Test.  Mat.,  1914, 
Part  II,  page  509).  Data  given  on  moisture,  vis- 
cosity, cost,  and  breaking  strength  of  25  samples  of 
glue. 


No. 

1.... 
2.... 
3.... 
4.... 

5.... 


TABLE  5— KEEPING  QUALITIES 

No. 


10 

11 

12 

13 

14 

15 

16 


Lab.  F 
Hours* 

142 
52 

142 

142 

142 

142 

142 
52 

218 

142 

97 

* 

218 


17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 


Lab.  F. 
Hours** 
334 
142 

* 

97 

* 

142 
142 

218 

97 
142 


*A11  samples  discarded  at  the  end  of  334  hours, 
marked  with  a  star  were  not  foul  at  this  time. 


Samples 

**Time  required  for  glue  to  develop  an  offensive  odor. 

TABLE  6. 
Typical  results  obtained  by  methods  recommended  in  appendix. 


u 

158 
155 
239 
157 
299 


218 
160 
175 
166 
273 
272 
153 
174 

*Peter   Cooper   Co.'s   standard,   1%.      **Peter  Cooper   Co.'s 
standard,  l*/4.    ***Bureau  Aircraft  Production  standard  sample. 


s£ 

si 

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83.1 

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24.1 

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89.3 

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24.3 

2644 

84 

2%-l 

89.9 

78% 

27.0 

2370 

42 

2%-l 

102.4 

97% 

27.5 

2660 

100 

2%-l 

102.8 

100% 

27.2 

109.7 

74% 

27.5 

118.8 

83% 

27.8 

145.0 

100% 

28.5 

3000 

148. 

101% 

2866 

86 

2     -1 

162.2 

100% 

23.8 

3010 

78 

23/4-l 

177.0 

100% 

30.6 

2880 

56 

2%-l 

180.6 

105% 

29.5 

3150 

88 

2     -1 

183.7 

107% 

2910 

75 

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201.8 

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29.0 

213.3 

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30.8 

2890 

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2*4-1 

259.5 

120% 

32.4 

2793 

69 

2*4-1 

CHAPTER  XII. 

GRADING  THE  GLUE  SAMPLE. 

AS  explained  before,  the  kinds  of  glue  that  may 
be  obtained  are  almost  infinite  in  variety.    In- 
deed, there  is  an  almost  unlimited  variation  in 
the  appearance  of  glue  samples.     Jerome  Alexander  GRADES  OF  GLUE 
(Jour.  Soc.  Chem.  Ind.,  1906,  25,  158)  states:  "In  glue,   SUGGESTED  BY 
above  all  things,  appearances  are  deceptive.  Even  after  JEROME 
a  manufacturer  has  finished  his  glue  he  is  obliged  to  ALEXANDER. 
test  it  in  order  to  establish  the  grade  of  his  finished 
product."   Alexander  grades  his  samples  by  standards 
which  he  keeps  in  his  laboratory.     He  states    (see 
above)  :    "The  choice  of  standards  is  a  very  important 
matter,  for  once  they  are  taken  all  unknown  glues  are 
measured  by  them.    Few  published  results  of  glue  tests 
can  be  used  for  comparison,  for  seldom  if  ever  have  any 
two  investigators  worked  on  the  same  glue  or  glues, 
which  have  been  described  sometimes  by  their  cost, 
sometimes  by  the  stock  from  which  they  were  manu- 
factured, and  upon  which  only  partial  determinations 
were  made.    That  definite  standards  will  simplify  and 
harmonize  the  grading  of  glue  is  self  evident. 

"We  arbitrarily  fix  sixteen  nearly  equidistant 
grades,  and  assign  to  them  values  running  from  10  to 
160,  allowing  ten  points  between  each  grade. 

160  80—13/8 

150  70—1/2 

140  60—1% 

130— A  Extra  50— 1% 

120—1  Extra  40— 1% 

110—1  30—2 

100—1  X  20 

90— VA  X  10 

"Opposite  these  grades  I  have  set  the  grades  es-  PETER  COOPER 
tablished  long  ago  by  Peter  Cooper,  which  are  used  GRADES. 
for  comparison  by  many  American  manufacturers  and 
dealers." 


78 


MODERN  GLUES  AND  GLUE  TESTING 


RELATION 
BETWEEN 
VISCOSITY    AND 
JELLY 
STRENGTH. 


The  following  determinations  were  made  to  es- 
tablish such  definite  figures  on  our  standards  as  will 
enable  anyone  to  pick  out  glues  of  the  same  character- 
istics. The  higher  standards,  from  60  up,  are  neutral 
hide  glues,  clear,  clean,  well  made,  free  from  any  odor 
of  decomposition,  and  practically  free  from  foam  and 
grease,  for  the  lower  standards,  bone  glues  were  chos- 
en, because  most  low  test  glues  show  abnormal  viscosi- 
ties. (The  viscosities  were  taken  in  the  apparatus 
described  in  Chapter  VI,  page  31.  See  original  article 
Jerome  Alexander  Jour.  Soc.  Chem.  Ind.,  1906,  25,  158, 
for  method.  The  jelly  strength  was  taken  as  described 
in  Chapter  VII,  page  37). 


10 
20 
30 

40 

50 

60 

70 

80 

90 

100 

110 

120 

130 

140 

150 

160 


16 

16^ 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

28 

34 

40 


60 
82 
104 
126 
148 
170 
192 
214 
236 
258 


1701 
2324 
2948 
3572 
4196 
4820 
5443 
6067 
6691 
7314 


Fernbach  states,  relative  to  the  grading  of  glues 
(Glues  and  Gelatines,  1907,  page  57)  :  "A  study  of 
viscosities  *  *  *  of  glues  confirms  what  has  already 
been  said  about  the  inadequacy  of  viscosity  as  the 
ultimate  measure  of  glue  strength.  The  author  has 
tested  more  than  thirty  thousand  samples  of  glue  and 
gelatine,  and  relying  invariably  on  the  finger  test  (jelly 
strength)  in  preference  to  using  any  test  machine.  The 
results  have  always  been  concordant." 


GRADING   THE   GLUE   SAMPLE 79 

In  general,  the  operator  in  grading  a  sample  must 
rely  mainly  upon  the  jelly  strength,  using  other  tests 
as  auxiliary  aids,  and  for  comparison,  must  have  in 
his  possession  samples  of  known  grades  with  which  to 
compare  his  unknown  test  sample.  He  will  find  in 
general  that  the  jelly  strengths  and  viscosities  are 
comparable,  or  in  other  words,  he  might  grade  on  the 
basis  of  either.  If  they  do  not  check  he  should  look  " 

. -  _  ...  _  .     .  _    .  .  THE    SAMPLE. 

upon  the  sample  with  much  suspicion  and  inquire  care- 
fully into  the  method  of  manufacture,  quality  of  stock 
used,  etc.,  before  accepting  the  glue.  In  normal  run 
glues,  jelly  strength  and  viscosity  are  the  only  tests 
absolutely  needed. 


See  also  Frost  and  Linder  (Proc.  Am.  Soc.  Test.  Mat.,  1914, 
page  509). 


CHAPTER  XIII. 

SOME  INTERESTING  STRENGTH  DATA  ON  GLUES. 

TESTS  on  joint  strengths  obtained  with  hide  glue 
on  a  number  of  species  showed  that  it  was  possible 
to  glue  them  without  obtaining  glue  failures  in  the 
test.    The  species  tested,  all  of  which  gave  successful 
results,  were  the  following : 

Hard  maple  Douglas  fir  African  mahogany       THESE  WOODS 

Yellow  birch  Red  oak  White  mahogany         GIVE  STRONG 

Black  walnut  White  oak  Tanguile 

Red  gum  Central  American  Black  cherry 
Yellow  poplar                   mahogany 

Similar  tests  on  greenheart  were  unsuccessful. 
Numerous  attempts  made  to  glue  this  wood  failed  in 
producing  a  strong  joint.  Similar  tests  made  on 
maple  coated  with  varnish,  shellac,  and  airplane  dope 
also  failed  to  give  good  joints.  The  conclusion  was 
that  it  was  dangerous  practice  to  try  to  glue  over 
wood  coated  with  these  materials.  It  is,  of  course,  pos- 
sible that  special  methods  could  be  devised  for  doing 
such  work  if  it  was  desirable.  Similar  tests  using  wood 
coated  with  lard  oil,  cylinder  oil  (mineral)  and  corn  oil 
were  made.  The  oils  were  rubbed  into  the  wood  with  a 
cloth  and  the  wood  allowed  to  stand  15  hours  before 
gluing.  While  no  definite  conclusion  could  be  drawn, 
the  results  were  surprisingly  good.  Specimens  coated 
with  all  of  these  oils  gave  quite  high  strength  values. 

Tests  on  plywood  glued  with  animal  glue  and  soaked  EFFECT  OF 
in  gasoline  and  in  engine  oil  indicated  that  these  oils  GASOLIXE  ON 
did  not  have  a  deleterious  effect  on  the  glue  joint  over  STRENGTH  OF 
a  period  of  15  days.     Subsequent  tests  over  a  period  JOINTS. 
of  4  months  showed  some  weakening  effect. 

The  common  assertion  that  scratched  surfaces  make 
stronger  glued  joints  than  smooth  surfacesjseems  hard 
to  prove.  Comparative  tests  made  on  several  occa-  ' 

•  i  i  -r-m  -r-k  f  ••*••••  JOINTS      VLRbUo 

sions  by  the  Forest  Products  Laboratory  all  indicate  SMOOTH. 
that  the  strengths  of  these  two  types  of  joints  are  prac- 
tically the  same. 


82 


MODERN  GLUES  AND  GLUE  TESTING 


The  test  specimens  used  by  the  laboratory  were 

pairs  of  hard  maple  blocks,  some  with  smooth  and 

TOOTH  PLANED    some  with  tooth-planed  contact  surfaces.    These  blocks 

JOINTS  ARE        were  glued  with  a  high  grade  hide  glue,  allowed  to 

NOT  ADVISED.      stand  for  a  week,  and  then  sheared  apart  in  an  Olson 

universal  testing  machine.     Four  joints  of  each  type 

were  compared  in  a  single  test. 

Eleven  such  tests  gave  the  following  average  re- 
sults: 


COMPARATIVE      STRENGTH      OF      SCRATCHED      AND 
SMOOTH  JOINTS 


Scratched  Joints 
Shear    Wood  Surface 
Test       Strength    in  Failure 
No.     Lbs.  sq.  in.     Per  cent. 
1  1787         25 
2  1366 

Smooth  Joints 
Shear  Wood  Surface 
Strength   in  Failure 
Lbs.  sq.  in.    Percent. 
1855 
943 
3086        50 
1571         25 
2416        100 
1678         62 
1800 
2455        100 
2180        25 
2395         62 
2520         75 

2040        47 

3  
4 

1976 
2409 
2298 
1947 
2310 
1835 
1425 
2330 
2180 

1988 

75 
100 
75 
12 
100 

35 

5  
6 

7  
8 
9  
10  
11  

Gen.  Av'g 

It  will  be  noted  that  in  seven  of  the  eleven  tests 
smooth  surfaces  gave  the  better  adhesion.  Consequent- 
ly it  would  seem  that  there  is  no  advantage  in  tooth- 
planing  wood  for  gluing  purposes. 

Some  interesting  points  have  been  brought  out  on 
the  gluing  of  laminated  construction,  particularly  air- 
plane propellers,  from  recent  experiments  made  at  the 
Forest  Products  Laboratory  at  Madison,  Wisconsin. 
HEATING  WOOD         Propellers  had  been  found  to  give  trouble  with 
BEFORE  GLUING   open  joints  when  made  of  certain  kinds  of  wood,  and 
GIVES  STRONGER  glued  with  certified  hide  glue.     Propellers  of  oak  and 
birch  very  frequently  had  open  joints,  while  mahogany 
propellers  could  be  satisfactorily  glued  even  without 
heating  the  laminations.     Heating  the  oak  and  birch 
laminations  before  gluing  was  found  to  give  firm  glue 
joints,  and  even  in  mahogany  as  well  it  was  found  that 


RETARDS 
SETTING    OF 
THE    GLUE. 


SOME  INTERESTING  STRENGTH  DATA  ON  GLUES 83 

if  the  laminations  were  heated  before  gluing,  the  joints 
were  more  uniform  in  strength.  All  propellers  in  which 
the  laminations  were  heated  before  gluing  gave  firm 
joints  which  showed  no  tendency  to  open  up. 

Heating  the  laminations  before  gluing,  however, 
was  found  to  seriously  retard  the  setting  of  the  glue. 
Strength  tests  were  made  on  large  sized  blocks  glued 
up  with  hide  glue  to  determine  what  effect  heating 
laminations  had  on  the  glue  strength.  The  tests  were 
made  about  10  days  after  gluing.  The  results  obtained 
on  this  test  are  shown  in  the  following  table : 

SHEARING  STRENGTHS  DEVELOPED  IN  LARGE  GLUED 
UP  BLOCKS   WHEN   UNDER   PRESSURE  FOR 

8,  10  AND  12  HOURS.* 
Central  American  Mahogany. 

8  hrs.  under  Press.  10  hrs.  under  Press.  12  hrs.  under  Press. 

Max.     Min.      Av.       Max.     Min.      Av.       Max.     Min.      Av. 

Cold  2489  1251  1949   2418  1446  1995   2098  1280  1645 

Hot  1735  1250  1567   1845  1160  1589   1788  1390  1635 

Northern  Red  Oak 

8  hrs.  under  Press.  10  hrs.  under  Press.  12  hrs.  under  Press. 

Max.  Min.   Av.   Max.  Min.   Av.   Max.  Min.   Av. 

Cold  2489  1251  1949   2418  1446  1995   2096  1280  1646 

Hot  2001  1250  1659   2150  1362  1739   2220  1542  1910 

Hard  Maple 

8  hrs.  under  Press.  10  hrs.  under  Press.  12  hrs.  under  Press. 

Max.     Min.      Av.       Max.     Min.      Av.       Max.     Min.      Av. 

Cold  3620  2367  3015   3170  1900  2751   3072  1815  2361 

Hot  3260   778  1652   3338  2124  2584   2960  2015  2576 

*  Strength  tests  made  10  days  after  gluing. 

While,  in  all  species  the  strength  of  the  hide  glue 
was  fully  developed  in  eight  hours  in  cold  blocks,  in 
hot  blocks  the  full  glue  strength  was  not  developed  in 
10  hours,  and  in  oak  even  in  12  hours,  an  increase  in 
strength  being  clearly  shown  for  an  increase  in  time 
under  pressure. 

High  density  woods  have  been  found  to  absorb 
heat  faster  and  in  greater  quantities  than  low  den- 
sity woods,  so  that  mahogany  showed  less  retarding 
effect  on  the  glue  than  the  oak  and  maple. 

Heating  laminations  has  been  shown  to  be  desirable 
in  order  that  open  joints  may  be  avoided,  while  at  the 
same  time  the  strength  distribution  becomes  more  uni- 
form. The  retarded  setting  of  the  hide  glue  requires 


84 


MODERN  GLUES  AND  GLUE  TESTING 


HIGH    GRADE 
GLUES     ARE 
MORE 
MOISTURE 
RESISTANT 
THAN  LOW 
GRADE  ONES. 


a  longer  pressure  period  to  develop  full  strength,  and 
under  the  conditions  prevalent  in  glue  rooms,  a  period 
of  12  hours  under  pressure  is  not  long  enough  to  de- 
velop the  full  strength  of  the  glue. 

That  there  is  a  close  relation  between  the  viscosity 
and  therefore  the  grade  of  animal  glues,  and  their  re- 
sistance to  loss  of  strength  in  moist  air,  is  strongly  in- 
dicated in  the  following  table,  which  gives  the  length 
of  time  different  glues  resisted  a  humidity  of  98  per 
cent. 

TE^T  1 


TEST  2 


TEST  3 


1. 


8 


>« 


1 

o 

13  
t7 

.  1.62 

i-s-o 
222 

ll 
2 

'   -  Z 

10% 

4 
4 

!«2«l  £ 

12 
12 

4 
4 

24 
24 

36  
34  
37  
35  
19  
21  
9  

1.70 
.  2.00 
.  1.92 
.  2.90 
.  4.98 
.  4.14 
.  5.48 

219 
267 
256 
315 
356 
338 
416 

2 
2 
2 
2 

4 

121/7 
17 
13 

42 
59% 

4 
4 

4 

4 
4 

14  % 
26% 

36 

48 
66% 

4 
4 

4 

4 

4 

24 

48 

44 

66 

198 

*In  this  test  the  specimens  were  kept  at  90  per  cent  humidity 
for  120  hours  (5  days). 
fThis  is  a  vegetable  glue. 

Specimens  of  V8-inch  birch  veneer  were  glued  two- 
ply  with  the  grain  parallel,  and  with  one  square  inch 
of  glued  surface.  The  specimens  were  suspended  in 
a  humidity  chamber  with  a  1-pound  weight  hung  on 
each,  and  the  time  required  for  failure  of  the  glue  joint 
was  noted.  Tests  one  and  two  were  made  at  98  per 
cent,  humidity.  In  test  three  the  specimens  were  kept 
at  90  per  cent,  humidity  for  120  hours,  when  the  hu- 
midity was  raised  to  98  per  cent.  No  failure  occurred 
at  90  per  cent.  The  temperature  was  about  80  deg. 
Fahr. 


CHAPTER  XIV. 

USE  AND  APPLICATION  OF  THE  GLUE   HYDROMETER. 

A  GLUE  hydrometer  is  an  instrument  for  meas- 
uring the   density   of  glue   solutions   and   ex- 
pressing the  results  in  terms  of  the  density  of 
water,    or    in    some    scale    such    as    Baume    degrees  THE  GLUE 
that  in  effect  also  express  results  in  terms  of  the  HYDROMETER. 
density  of  water.    Since  the  density  of  both  glue  solu- 
tions and  water  vary  with  temperature,  hydrometer 
readings  must  take  accurate  account  of  temperature. 

The  glue  hydrometer  usually  employed  consists  of 
a  copper  pot  and  a  hydrometer  arranged  for  temper- 
ature of  75°  C.,  or  167°  F.  The  melted  glue  is  poured 
into  the  copper  receptacle  and  the  hydrometer  is  al- 
lowed to  sink  until  it  finds  its  position.  Some  experts 
employ  what  is  known  as  Weinhagen's  Hydrometer. 
This  is  provided  with  a  thermometric  correction  scale 
at  the  top  of  the  instrument,  and  this  is  always  clear 
of  the  liquid  when  the  hydrometer  is  immersed.  The 
temperature  must  be  adjusted  accurately  before  mak- 
ing the  determination. 

This  instrument  is  used  to  determine  water  ab-  THE 
sorption.    It  is  also  used  when  inspecting  glue  rooms,  HYDROMETER 
determining  the  amount  of  water  and  glue  used  by  DOES  NOT  SHOW 
immersing  the  instrument  into  the  glue  solution  in  THE  QUALITY 
the  tanks,  cookers  or  glue  pots.     This  also  affords  a  OP  THE  GLUE- 
very  good  check  on  the  loss  due  to  evaporation.    This 
instrument  cannot  be  used  to  determine  glue  quality, 
as  its  readings  have  no  bearing  whatever  on  viscosity 
or  adhesiveness. 


APPENDIX  TO  BOOK  I 

MODERN  GLUES  AND 
GLUE  TESTING 

METHODS  OF  TESTING 
ANIMAL  GLUE 


IN  USE  AT  THE 

FOREST  PRODUCTS  LABORATORY 
MADISON,  WISCONSIN 


APPENDIX. 

METHODS  OF  TESTING  ANIMAL  GLUE  IN  USE  AT  THE 
FOREST  PRODUCTS  LABORATORY.* 

DURING  the  war  all  the  glue  for  use   in  air- 
craft  construction  was  tested  by  the  Bureau 
of  Aircraft  Production  inspectors  at  the  Forest 
Products    Laboratory,    Madison,    Wis.      More    than 
a  million  pounds  of  hide  glue  furnished  by  ten  differ-  OYER  ONE 
ent   manufacturers   had    to    be    examined   before    its  MILLION 
shipment  to  the  various  aircraft  factories  was  permit-  POUNDS  OF 
ted.    This  is  not  the  first  attempt  which  has  been  made  GLUE  INSPECTED 
to  introduce  standards  in  the  glue  trade,  but  it  is  the  BY  THESE 
first  instance  in  which  the  majority  of  the  large  manu-  METHODS. 
facturers,  as  well  as  many  of  the  purchasers  of  glue, 
have  recognized  the  same  standards  and  assented  to  the 
validity  of  the  same  methods  of  testing. 

The  methods  which  were  adopted  were  selected  as 
being  those  of  rational  basis,  direct  practical  bearing, 
simplicity  and  convenience.  They  are  not  ideal ;  a  few 
of  them  are  scarcely  satisfactory.  Nevertheless,  when 
properly  applied  and  interpreted,  they  will  enable  the 
chemist  to  select  and  grade  glue. 

The  physical  constants  of  glues  and  glue  solu- 
tions cannot  be  measured  with  the  same  precision  as 
those  of  most  of  the  materials  which  the  chemist  is 
called  upon  to  test.  Glue  is  a  substance  of  widely 
varying  chemical  composition  and  physical  condition. 
Tests  made  upon  it  are  profoundly  affected  by  factors 
which  are  difficult  to  control.  Time,  temperature, 
colloidal  condition  and  the  effects  of  micro-organisms 
are  unusually  important  in  glue  testing. 

The  methods  which  were  adopted  are  as  follows: 

For  accurate  work  the  viscosity,  jelly  strength  and 
jelly  melting  point  determinations  should  be  made  upon 
a  sample  which  has  been  carefully  dried  at  a  low 
temperature  to  constant  weight.  The  precaution,  how- 
ever, is  frequently  disregarded. 


*From  paper  prepared  by  Wilbur  Lloyd  Jones,  senior  inspec- 
tor, B.  A.  P. 


90 


MODERN  GLUES  AND  GLUE  TESTING 


Weigh  out  50  grams  of  ground  glue  and  add  it  to 
250  c.  c.  of  cold  water.  Allow  the  mixture  to  stand  for 
two  or  three  hours  in  an  ice  box  and  keep  the  breaker 
containing  the  mixture  covered  with  a  watch  glass. 
Then  place  the  breaker  in  the  water  bath  and  raise  the 
temperature  gradually  to  60°  C.,  stirring  every  once  in 
DETAILED  a  while.  Keep  the  watch  glass  in  place  when  the  mixture 

METHOD  FOB  is  not  being  stirred  in  order  that  the  moisture  which  es- 
VISOOSITY.  capes  from  the  solution  may  be  condensed.  When  the 
lumps  have  disappeared  from  the  solution,  recover  the 
drops  of  condensed  moisture  on  the  watch  glass  and 
strain  the  solution  through  a  piece  of  cheese  cloth  or 
wire  gauze.  Then  cover  once  more  with  the  watch 
glass  and  allow  the  solution  to  remain  in  the  water 
bath  until  the  temperature  of  the  water  in  the  annular 
ring  of  the  viscosimeter  is  about  60°  C.  An  Engler 
viscosimeter  is  used.  Place  a  200  c.  c.  viscosimeter 
flask  underneath  the  orifice  of  the  viscosimeter.  Then 
pour  the  glue  solution  into  the  cup  of  the  viscosimeter 
until  it  just  covers  each  of  the  three  level  points,  and 
adjust  the  thumb  screws  on  the  stand  of  the  viscosi- 
meter so  that  the  instrument  is  perfectly  level.  This 
should  be  done  as  quickly  as  possible  in  order  that  loss 
of  moisture  from  the  solution  will  be  at  a  minimum. 
Then  place  the  cover  on  the  viscosimeter,  insert  the 
thermometer  and  regulate  the  temperature  so  that  the 
glue  solution  in  the  cup  is  exactly  60°  C.,  and  the  water 
in  the  jacket  is  somewhere  between  60°  and  61°  C.  Then 
remove  the  wooden  plug  with  one  hand  and  snap  the 
stop  watch  with  the  other,  and  allow  the  glue  solution 
to  flow  until  the  meniscus  is  exactly  opposite  the 
200  c.  c.  mark  on  the  flask.  Then  snap  the  stop  watch 
again  and  note  the  reading.  The  viscosity  of  the  solu- 
tion is  the  number  of  seconds  required  for  200  c.  c.  of 
solution  to  flow  at  60°  C.  through  the  standard  orifice 
of  the  viscosimeter.  Before  making  a  second  deter- 
minAtion,  clean  out  the  apparatus  thoroughly  and  be 
sure  that  no  glue  remains  in  the  orifice,  nor  on  the 
wooden  plug.  The  tests  for  odor,  reaction,  foam,  jelly, 
melting  point,  and  grease  should  be  made  on  the  residue 
left  from  the  viscosity  determination. 

The  odor  is  determined  by  smelling  the  liquid. 


METHODS   OF   TESTING  ANIMAL   GLUE 91 

Take  a  piece  of  red  and  a  piece  of  blue  litmus  and  THE  REACTION. 
dip  both  into  the  glue  solution.  Remove  them  and 
examine  for  change  of  color.  If  the  blue  litmus  turns 
red  or  reddish,  the  solution  is  acidic.  If  the  red  litmus 
turns  blue,  the  solution  is  alkaline.  Glue  solutions  are 
usually  either  slightly  acidic  or  neutral. 

The  glue  solution  is  then  placed  in  a  water  bath  FOAM. 
and  heated  to  60°  C.  It  is  agitated  by  a  stirrer  at- 
tached to  a  small  electric  motor  for  exactly  one  min- 
ute, after  which  time  it  is  allowed  to  stand  for  ex- 
actly one  minute.  The  height  of  the  foam  is  then 
measured. 

The  residue  is  then  warmed  up  once  more  in  the  GREASE. 
water  bath  and  a  small  quantity  of  an  aqueous  solu- 
tion of  a  dye  is  added  to  it.  A  brush  is  then  care- 
fully cleaned  until  it  is  free  from  every  trace  of 
grease.  A  test  is  made  on  the  brush  by  dipping  it 
into  a  small  portion  of  a  dye  solution  and  painting  a 
broad  streak  upon  a  clean  sheet  of  unglazed  white 
paper.  If  the  colored  streak  is  free  from  spots  where 
the  color  has  been  repelled  from  the  paper,  the  brush 
is  sufficiently  clean  to  proceed  with  the  grease  test. 
The  brush  is  placed  in  the  glue  solution  now  colored 
with  dye  and  several  streaks  are  painted  upon  clean 
unglazed  white  paper,  employing  a  moderate  amount  of 
glue  solution  in  the  brush  each  time.  The  number 
of  "eyes"  in  the  colored  streaks  indicates  the  amount  of 
grease  in  the  glue.  (See  pages  33  and  34.) 

The  instrument  which  is  in  use  at  the  Forest  Pro-  JELLY 
ducts  Laboratory,  Madison,  Wisconsin,  for  determin-  STRENGTH. 
ing  the  jelly  strength  of  glues,  is  a  modified  form  of 
an  apparatus  which  is   used  for  the  same  purpose 
in  the  laboratory  of  one  of  the  large  glue  manufactur- 
ing companies. 

It  is  essentially  a  "float"  which  rests  lightly  on 
the  surface  of  a  jelly,  and  a  "plunger,"  to  which  is 
attached  a  scale  by  means  of  which  the  depth  of  pen-  A  NEW  METHOD 
etration,  or  rather,  depression,  can  be  measured.  FOR  JELLY 

The  "float"  is  made  of  brass  plate.     It  should  not   STRENGTH. 
weigh  more  than  200  grams.     The  bottom  surface, 
which  comes  in  contact  with  the  jelly,  should  be  rather 
large,  in  order  to  distribute  the  weight  and  to  prevent 


92 MODERN  GLUES  AND  GLUE  TESTING 

the  float  itself  from  depressing  the  jelly  to  any  appre- 
ciable extent.  At  the  top  of  the  "float"  there  is  a 
guide  of  rectangular  cross  section  through  which  the 
standard  or  scale  of  the  "plunger"  moves  freely.  An 
inverted  trianguler  section  (1  c.  m.  in  altitude)  is  cut 
away  from  the  top  of  the  front  face  of  this  guide,  and 
the  resulting  diagonal  line  is  divided  into  10  equal  parts 
in  order  to  enable  the  operator  to  read  the  depression 
of  the  standard  to  tenths  of  a  centimeter,  and  to  esti- 
mate it  to  hundredths. 

THE  PLUNGER.  The  nose  of  the  "plunger"  is  hollow  so  that  it  can 
be  filled  with  shot,  and  the  weight  of  the  plunger  alter- 
ed at  will.  The  hole  through  which  the  shot  are  added 
or  withdrawn  is  closed  with  a  screw.  The  standard  is 
graduated  in  centimeters,  and  the  zero  mark  on  the 
standard  is  located  at  that  point  which  is  opposite  the 
zero  mark  on  the  graduations  on  the  "float"  when  the 
nose  of  the  "plunger"  is  resting  on  a  perfectly  level 
surface.  These  details  are  explained  in  Fig.  17. 

This  instrument,  when  used  to  test  12  to  1  jellies, 
has  been  found  to  be  very  delicate  if  the  total  weight 
of  the  "plunger"  is  250  grams.  To  raise  the  weight 
of  the  "plunger"  to  this  amount,  a  brass  weight,  a 
drawing  of  which  will  be  found  in  the  plan,  will  have 
to  be  placed  on  top  of  the  nose. 

In  making  jelly  tests,  this  apparatus  is  used  as 
follows : 

Exactly  25  grams  of  ground  glue  are  added  to  300 
c.  c.  of  cold  water.  The  mixture  is  stirred,  covered 
with  a  watch  glass  and  allowed  to  stand  in  an  ice 
box  for  two  or  three  hours.  At  the  end  of  this  time 
the  mixture  is  placed  in  a  water  bath  and  heated  grad- 
ually to  60°  C.,  stirring  frequently  but  keeping  the 
beaker  covered  with  the  watch  glass  to  prevent  evap- 
oration. When  the  solution  is  free  from  lumps,  the 
condensed  moisture  is  returned  to  the  solution  and  the 
.  glue  is  poured  into  a  crystallizing  dish  of  standard 
size  and  shape.  A  dish  which  is  S1/^  inches  in  diameter 
and  2  inches  deep  will  be  found  very  convenient  for 
this  purpose.  The  depth  of  the  layer  of  glue  in  the 
crystallizing  dish  should  be  exactly  the  same  in  every 
case.  The  crystallizing  dish  with  its  contents  is  then 


METHODS   OF   TESTING  ANIMAL  GLUE 


93 


94 


MODERN  GLUES  AND  GLUE   TESTING 


DETERMINING 

JELLY 

STRENGTH. 


KEEPING 
QUALITIES. 


JELLY 
MELTING  POINT. 


placed  in  an  ice  box  at  from  5°  to  10°  C.,  for  12  or  15 
hours.  At  the  end  of  this  time  it  is  removed  and  the 
jelly  strength  of  the  glue  is  determined  immediately. 
This  is  done  by  comparison.  A  sample  of  standard 
glue  should  be  treated  in  exactly  the  same  way  as  des- 
cribed above  and  at  exactly  the  same  time  as  the  glue 
which  is  being  studied.  The  glue  being  tested  and  the 
standard  should  be  removed  from  the  ice  box  at  the 
same  time  and  the  jelly  strength  first  determined  by 
pressure  with  the  fingers.  Then  the  brass  jelly  tester 
should  be  employed  and  3  or  4  readings  of  the  amount 
of  penetration  determined.  Obviously  the  weaker  the 
jelly  the  greater  will  be  the  depth  to  which  the  plunger 
will  penetrate. 

The  depression  of  the  250-gram  plunger  against 
the  resistance  of  the  jelly  is  measured  in  millime- 
ters, and  compared  with  the  corresponding  depres- 
sion of  the  plunger  in  the  case  of  the  standard  glue. 
The  consistency  of  the  jelly  is  obviously  inversely 
proportional  to  the  depth  of  depression.  This,  of 
course,  is  true  only  in  a  more  or  less  crude  way;  it 
is  not  an  exact  mathematical  relationship. 

This  test  will  be  found  to  be  as  delicate,  if,  in- 
deed, not  more  so,  than  the  so-called  finger  test.  Jelly 
strength  is  expressed  in  percentages  and  it  is  equal  to 
100  times  the  amount  of  penetration  in  the  standard 
glue  divided  by  the  amount  of  penetration  in  the  glue 
being  tested. 

The  jelly  resulting  from  the  above  test  is  then 
allowed  to  stand  uncovered  in  the  laboratory  at  room 
temperature  for  48  hours,  at  the  end  of  which  time 
the  skin  on  the  surface  is  broken  and  the  odor  of  the 
jelly  is  noted.  Even  after  48  hours  the  odor  should 
be  sweet. 

To  determine  the  melting  point  of  a  jelly  the  fol- 
lowing procedure  is  employed:  A  12-inch  length  of 
6-millimeter  glass  tubing  is  bent  in  the  middle  so  as 
to  form  a  U-tube. 

A  drop  of  hot  glue  solution  (5  parts  of  water  to 
1  of  glue)  is  introduced  into  one  arm  of  the  U-tube.  A 
stirring  rod  or  a  medicine  dropper  can  be  used  con- 
veniently for  this  purpose.  If  a  12-to-l  jelly  were 


METHODS   OF   TESTING  ANIMAL   GLUE 95 

used  a  more  sharply  defined  melting  point  might  be 
obtained,  but  its  behavior  would  be  farther  removed 
from  the  concentrated  solutions   which  are   used  in 
gluing  practice,  and  it  would  accordingly  be  of  less  DETAILS  OF 
significance.     When  the  drop  of  glue  has  sunk  to  a  MELTIXG 
certain  mark  which  has  been  etched  half  way  down  POINT  ^ 
one  side  of  the  tube,  the  opening  of  the  other  arm 
is  closed  with  the  fore-finger,  and  the  tube  quickly 
plunged  in  ice  water.    The  glue  will  now  be  found  to 
be   stationary,   a   cylinder   of  jelly   exactly   opposite 
a  fixed  mark  on  the  tube.    It  is  important  that  there 
should  be  no  glue  in  any  other  part  of  the  tube,  be- 
cause it  might  clog  the  bore  and  subsequently  prevent 
the  free  movement  of  the  cylinder  of  glue. 

The  U-tube  with  its  cylinder  of  jelly  is  allowed 
to  stand  about  an  hour  at  10°  to  15°  C.  It  is  then 
immersed  in  a  beaker  of  water  (10°  to  15°  C.)  to 
such  a  depth  that  the  glue  is  beneath  the  level  of  the 
surface  of  the  water.  The  temperature  is  then  slowly 
raised  and  the  water  stirred  constantly.  The  tube  is 
fastened  to  a  sensitive  thermometer  by  means  of  rubber 
bands.  At  a  certain  definite  temperature  the  cylinder 
of  jelly  will  commence  to  slip  from  its  position,  sink- 
ing slowly  at  first.  The  temperature  at  which  movement 
is  first  noticeable  is  taken  as  the  melting  point.  The 
heat  communicated  from  the  walls  of  the  tube  melts  the 
surface  of  the  cylinder  of  jelly  which  is  in  contact  with 
it,  thereby  allowing  the  jelly  to  fall  of  its  own  weight. 
Glue  jelly  is  a  very  poor  conductor  of  heat.  Conse- 
quently, other  methods  which  require  the  thermal 
penetration  of  a  considerable  mass  of  jelly  will  be 
handicapped  on  that  account. 

The  adhesive  or  strength  test  is  carried  out  as 
follows :  A  piece  of  hard  maple  is  cut  into  two  ADHESIVENESS. 
halves  of  the  size  and  shape  indicated  by  the  first 
specimen  in  Fig.  6.  Dense,  hard,  straight-grained, 
thoroughly  seasoned  wood,  free  from  defects,  should 
be  used.  Preferably  it  should  be  flat-sawed  lumber. 
The  two  blocks  should  be  put  through  the  planer  and 
then  over  the  jointer.  The  surfaces  which  are  to  be 
placed  in  contact  should  be  absolutely  flat,  and  they 
should  fit  perfectly.  The  moisture  content  should  be 


96 


MODERN  GLUES  AND  GLUE  TESTING 


PREPARATION 
OF   BLOCKS 
FOR  STRENGTH 
TESTS. 


GLUE  APPLIED 
AT    FOUR 
DIRECTIONS. 


PRESSURE 
MUST  BE 
MODERATE. 


between  6  and  13  per  cent.  It  has  been  found  unneces- 
sary to  warm  the  test  blocks  above  the  temperature  of 
the  room.  Moreover,  it  is  undesirable,  because  even 
a  moderate  heating  is  liable  to  distort  the  blocks  to  a 
certain  extent  and  prevent  them  from  fitting  together 
perfectly. 

It  is  a  good  plan  to  test  every  unknown  glue  at  four 
different  water^glue  ratios.  With  a  moderately  high 
grade  glue,  such  as  Peter  Cooper's  Standard  No.  1, 
sets  of  specimens  should  be  prepared,  using  2,  2^4,  2l/2 
and  234  parts  of  water  respectively  to  one  part  of 
glue.  It  might  be  advisable  in  the  case  of  an  exceeding- 
ly high  grade  glue  to  prepare  a  test  block  at  3  to  1, 
and  there  are  low  grade  glues  which  will  give  best 
results  with  less  than  2  parts  6f  water  to  1  of  glue. 

The  glue  solution  should  be  used  as  soon  as  pos- 
sible after  it  has  melted  and  attained  a  temperature 
of  140°  to  150°  F.  The  glue  should  be  applied  freely 
to  both  of  the  surfaces  which  are  to  be  joined.  It 
often  helps  considerably  if  the  hot  glue  is  brushed  well 
into  the  wood,  to  assure  proper  penetration  by  the  glue. 
The  blocks  should  then  be  allowed  to  stand  until  the 
glue  has  thickened  a  little,  but  they  should  not  stand 
long  enough  for  the  glue  to  "set."  If  the  glue  is 
touched  from  time  to  time  by  a  finger  which  is  rather 
quickly  withdrawn,  there  will  come  a  time  when  fibers 
or  strings  of  glue  an  inch  or  two  in  length  will  be 
pulled  up  from  the  surface.  When  this  point  has  been 
reached,  the  two  blocks  should  be  joined,  rubbed  to- 
gether slightly  with  light  pressure,  and  then  placed 
in  a  press  designed  in  such  a  way  as  to  assure  an  even- 
ly distributed  pressure.  As  soon  as  possible  the  pres- 
sure should  be  applied.  It  should  be  a  moderate  pres- 
sure, just  sufficient  to  bring  the  edges  of  the  glued 
surfaces  into  approximate  contact.  It  should  be  re- 
membered that  for  testing  purposes  it  is  better  to  em- 
ploy too  little  pressure  than  too  much. 

By  working  rapidly  one  can  prepare  joints  at  four 
different  concentrations  for  any  glue,  stack  them  in 
the  press  so  that  they  will  all  be  subjected  to  the  same 
pressure,  and  finish  the  adjustment  before  the  joint 
which  was  glued  first  has  been  "set." 


METHODS   OF   TESTING  ANIMAL   GLUE 97 

These  joints  should  be  left  in  the  press  for  at 
least  15  hours.  They  may  be  then  removed  and  placed 
in  a  drying  rack,  where  they  should  remain  for  at 
least  six  additional  days.  At  the  end  of  that  time 
they  may  be  cut  into  shear  blocks,  as  shown  in  Figs. 
5  and  6. 

These  shear  blocks  are  then  tested  in  an  Olsen 
Universal  Testing  Machine  (Fig.  8),  provided  with 
a  special  shearing  tool  as  shown  in  Fig.  7.  The  load 
should  be  applied  at  a  rate  not  to  exceed  .025  inch 
per  minute.  A  shearing  strain  is  brought  to  bear 
on  the  layer  of  glue  between  the  two  wooden  halves  of 
the  specimen.  At  a  certain  load  each  shear  block  will 
fail,  and  the  failure  will  be  either  in  the  glue,  in  the 
wood,  or  in  both.  The  load  at  which  failure  took 
place  and  the  exact  area  of  fracture  are  measured.  The 
shearing  stress  in  pounds  per  square  inch  can  then  be 
calculated. 

It  is  obvious  that,  whenever  the  failure  occurred 
in  the  wood  exclusively,  the  glue  would  have  resisted 
a  force  somewhat  greater  than  the  one  applied.  It 
is  only  when  the  failure  is  in  the  glue  entirely  that 
its  shearing  strength  has  been  fairly  determined.  It 
is  more  than  probable  that  the  higher  the  percentage 
the  amount  of  failure  in  the  wood  assumes,  the  FAILURE  HAS 
greater  will  be  the  disparity  between  the  actual  SIGNIFICANCE. 
strength  of  the  glue  and  the  load  at  which  failure  took 
place.  A  specimen  which  failed  at  2,000  pounds  per 
square  inch,  90  per  cent,  of  the  fracture  being  in  the 
wood,  might  indicate  a  stronger  glue  than  one  failed 
at  2,500  pounds  per  square  inch  where  only  10  per 
cent,  of  the  fracture  was  in  the  wood. 


Book  II 

GLUE  ROOM  EQUIP- 
MENT AND  THE  USE 
OF  GLUE 


BY 

C.  MORTIMER  BEZEAU 


Book  II 

TABLE  OF  CONTENTS 
CHAPTER  XV— Preparing  the  Wood  for  the  Glue 

The   Lumber — Storage — Test   for   Dryness — Warming 

the  Lumber — Ideal  Gluing  Temperature 105 

CHAPTER  XVI — Preparation  of  Core  Stock 

The  Core  Stock  Free  from  Checks — Crossbanding — 
Allowing  the  Crossbanded  Core  to  Dry — Right  and 
Wrong  Sides — Conditions  Affecting  Thickness 109 

CHAPTER  XVII— Preparing  Glue  for  Use 

The  Glue  Mixer— Soaking  Glue— Regarding  "Cook- 
ing"—The  Glue  Heater— The  Cleaning  Vat^-Use  of 
Pure  Water — Rainwater — Soda  in  Water — Use  of  a 
Glue  Size — Regarding  the  Changing  of  Brands 115 

CHAPTER  XVIII— Ideal  Surface  for  Gluing 

Hardwoods  —  End  Grain  —  Edge  Gluing  —  Concave 
Edges  123 

CHAPTER  XIX — Covering  Capacity  of  Glue 

High  Grade  Glue — Spread  Costs — Wastage — Efficiency     127 

CHAPTER  XX — Glue  Room  Equipment 

Modern  Appliances — Kinds  of  Cauls — To  Prevent  Glue 
from  Sticking  to  Cauls 131 

CHAPTER  XXI — An  Ideal  Glue  Room 

Ground  Floor  Location — The  Heaters — Ventilation — 
Drying  Room — Circulation  of  Air 135 

CHAPTER  XXII — Evolution  of  Glue  Room  Practice 

History — Progress — Unsolved  Problems — Conditions  in 
Europe  141 


102  MODERN  GLUES  AND  GLUE  TESTING 


CHAPTER  XXIII— Glue  and  Finishing  Departments 

Shifting  of  Responsibility— Blisters— Effect  of  Water 
on  Veneers — Loose  Veneer — An  Example  of  Trouble — 
Playing  the  Game  Square 145 


CHAPTER  XXIV—  Veneering  Scroll  Work 

Regarding     Designs — Elimination     of     Difficulties — A 
Lesson  for  Beginners — Thickness  of  Veneer. 149 


CHAPTER  XXV — Laying  Fine  Face  Veneers 

Importance  of  Good  Veneer — The  Redryer — The  Hot 
Box — Taping  Veneer — Spreading  the  Glue — Open 
Joints — Use  of  Warm  Cauls ...  153 


CHAPTER  XXVI— Spreading  the  Glue 

Evenness  is  Essential — Intelligence — Regarding  Foam 
—Good  Glue  is  Necessary 161 


CHAPTER  XXVII— The  Glue  Salesman 

The  Science  of  Salesmanship — Know  Your  Line  and 
Don't  Knock  the  Other  Fellow's — Friendship— Sales- 
Tests  —  Enthusiasm  —  Order  Takers  —  Competitors  — 
Service  —  Kinds  of  Salesmen  —  Advertising  —  Form 
Letters  and  Trade  Papers 165 


CHAPTER  XXVIII— Buying  and  Selling  Glue 

Purchasing   Department — Quality  vs.   Price — Requisi- 
tions—Recording Tests  175 


CHAPTER  XXIX— Paper  Box  Adhesives 

Selection  of  Glue — Box  Making  Machines — Silicate  of 
Soda  ...  .     179 


CHAPTER  XXX— Avoid  Abuses 

Good  Glue — Glue  Room  Temperature — Weighing — 
Boiling  of  Water — Correct  Temperature — Melting — 
Freezing — Co-operation  181 


CHAPTER  XV. 

PREPARING  THE  WOOD  FOR  THE  GLUE. 

TO  obtain  the  best  results  in  the  glue  room  it  is  not 
enough  that  the  glue  be  properly,  prepared  for 
the  wood;  it  is  equally  necessary  to  have  the  THE  LUMBER 
wood  properly  prepared  for  the  glue.  This  prepara-  SHOULD  BE 
tion  should  commence  early  in  the  process  of  making  PREPARED 
lumber — as  far  back  as  the  time  when  the  tree 
is  cut  down  in  the  forest.  Trees  should  preferably  be 
cut  during  the  late  fall  and  winter  months,  for  at  this 
time  the  trees  are  dormant  and  fairly  free  from  sap.  If 
the  tree  is  cut  down  during  the  spring  or  summer 
months  when  it  is  in  the  growing  stage  the  wood  is 
very  susceptible  to  atmospheric  changes;  and  the  con- 
tinual expanding  and  contracting  of  the  wood  is  very 
detrimental  to  the  life  of  a  glue  joint.  Much  of  this  dif- 
ficulty may  be  overcome  by  allowing  the  lumber  to  dry 
or  season  for  several  years.  However,  long  air  season- 
ing is  no  longer  feasible,  and  kiln  drying  is  usually  re- 
sorted to. 

Every  factory  should  have  a  place  for  storing  lum- 
ber between   the   dry-kiln   and   the  workshop.    This 
storehouse  should  be  well  ventilated  so  that  the  air  will  STORED  AFTER 
be  occasionally  changed — fresh  air  entering  from  the  LEAVING 
outside;  which  will  give  it  the  right  humidity.    The  KILN 
lumber  should  be  made  quite  dry  in  the  dry-kiln  before 
being  placed  in  this  storehouse,  which  should  be  kept 
at   a  temperature  of  about   60   degrees   Fahrenheit, 
which  temperature,  together  with  the  humidity  in  a 
properly  ventilated  place,  will  enable  the  lumber  to  so 
adjust  itself  that  it  will  become  less  changeable  in  its 
nature  and  less  prone  to  yield  to  atmospheric  influ- 
ences,  and,   therefore,   more   dependable  after   it   is 
worked  up. 

In  order  to  save  extra  handling  of  the  lumber, 
tracks  should  be  laid  in  the  storehouse  so  that  it  may 
receive  the  loaded  cars  direct  from  the  dry-kiln;  and 
then  in  turn  send  them  to  the  cutting-out  department 


106 


PREPARING  THE  WOOD  FOR  THE  GLUE 


TEST  LUMBER 
FOR 

DRYNESS 


WARM  THE 
LUMBER  IF 
GOLD 


without  any  changes.  If  this  cannot  be  done  the  lum- 
ber must  be  piled  with  strips  between  each  layer  the 
same  as  when  piling  for  the  dry-kiln. 

Lumber  should  always  be  tested  for  dryness  before 
being  glued  up.  If  unfit  stock  be  worked  up  it  will 
never  be  made  right  and  will  always  be  a  source  of 
trouble. 

A  method  of  testing  lumber  for  moisture  by  no 
means  uncommon  is  by  carefully  measuring  the  width, 
then  heating  it  in  an  oven  or  hot-box  and  noting  the 
amount  of  shrinkage.  But  this  is  not  a  safe  test.  The 
better  method  is  to  weigh  a  small  piece  on  a  very  sensi- 
tive scale ;  and  after  heating  in  an  oven  at  about  215° 
F.,  for  twenty-four  hours,  note  the  change  in  weight. 
Before  weighing  the  second  time  the  board  should  be 
allowed  to  cool  to  the  same  temperature  as  when  it  was 
first  weighed.  Heating  in  the  oven  should  eliminate  the 
last  particle  of  moisture  and  the  difference  in  weight 
before  and  after  heating  should  give  the  percentage  of 
moisture  which  the  lumber  contains. 

Lumber  should  never  be  glued  up  when  cold, 
whether  it  be  edge  jointing  or  veneering;  and  whether 
it  be  animal  or  vegetable  glue  that  is  to  be  used,  it  will 
be  safer  to  warm  the  wood  if  it  is  cold.  This  is  due  to 
the  fact  that  the  cold  glue  solution,  or  one  that  is 
chilled  by  cold  wood,  is  too  viscuous  to  permit  the  glue 
to  enter  the  pores  and  obtain  a  hold.  However,  care 
must  be  taken  not  to  overdo  the  heating.  The  best  re- 
sults are  obtained  between  80°  F.  and  95°  F. 

All  things  must  work  in  harmony  in  order  to  pro- 
duce the  best  results,  and  the  temperature  of  the  room 
in  which  the  work  is  done  must  be  in  harmony  with 
the  required  temperature  of  the  wood,  as  well  as  the 
temperature  of  the  glue.  There  was  a  time  when  a 
great  many  people  had  the  idea  that  the  higher  the 
temperature  of  the  glue-room  the  better;  with  the 
result  that  the  temperature  was  such  as  to  be  detri- 
mental to  the  health  of  the  workmen.  All  this  was  in 
harmony  with  the  other  mistaken  idea  that  glue  itself 
had  to  be  prepared  and  used  at  a  high  temperature. 
But  careful  experiments  show  that  a  temperature  suit- 


PREPARING   THE   WOOD   FOR   THE   GLUE  107 

able  for  the  workmen  is  suitable  for  the  work.    Such  a 
temperature  is  from  70  degrees  to  75  degrees  Fahren- 
heit. While  this  temperature  is  sufficiently  high,  under  AN  AVERAGE 
no  circumstances  should  the  glue  be  used  at  a  lower  TEMPERATURE 
temperature.  It  is  not  enough  to  have  the  glue  hot  and 
wood  warm,  because  the  cold  air  will  chill  the  outer 
surface  of  the  spread  and  impair  its  power  of  adhesion. 

The  temperature  here  indicated  is  the  one  to  be 
maintained  at  the  point  of  contact  between  the  air  and 
the  glue.  For  this  reason  the  thermometer  should  be 
on  a  level  with  the  glue  spreader  and  veneer-laying 
bench.  A  few  feet  in  height  frequently  makes  a  differ- 
ence of  several  degrees  in  the  temperature  of  the  air, 
especially  during  the  period  of  early  morning  heating 
before  the  warm  air  has  been  diffused  uniformly 
through  the  whole  room.  For  this  reason,  if  the  ter- 
mometer  is  placed  higher  than  the  point  of  contact  be- 
tween the  air  and  the  glue,  one  is  liable  to  begin  opera- 
tions in  a  temperature  several  degrees  lower  than  that 
required,  thereby  injuring  the  work  without  know- 
ing it. 

With  the  temperature  of  the  air  at  75  degrees  Fahr- 
enheit, the  wood  at  95  degrees  and  the  glue  at  140  de-  IDEAL 
grees,  we  have  that  ideal  combination  which,  every-  GLUING 
thing  else  being  equal,  will  insure  the  best  possible  COMBINATION 
results. 


CHAPTER  XVI. 

PREPARATION  OF  CORE  STOCK. 

IN  the  process  of  building  up  reinforced  wood  bodies 
for  pianos,  furniture,  automobiles  and  interior 
trim  there  is  what  is  called  a  "core,"  or  center ;  the 
proper  preparation  of  which  is  of  great  importance  to 
the  finished  article.  This  center,  being  the  foundation 
of  the  structure,  must  be  right ;  otherwise  the  quality 
of  the  finished  article  will  be  defective.  It  has  been  THE  CORE 
thought  by  some  that  the  core  being  covered  by  outer 
layers  requires  little  attention,  as  all  defects  in  mate- 
rial and  workmanship  are  hidden  from  view,  and  will 
never  be  revealed,  but  a  greater  fallacy  can  scarcely  be 
conceived.  Of  course,  this  core  does  not  require  the 
same  high  quality  of  material  that  is  needed  for  the 
outer,  or  face  layer;  but  the  contention  that  anything 
is  good  enough  for  corestock  is  the  one  we  wish  to 
combat. 

Core  stock  should  be  sound,  and  may  be  of  almost 
any  kind  of  wood  grown  on  this  continent ;  the  kind  to 
be  used  depending  entirely  on  the  use  to  which  the 
finished  article  is  to  be  put.  Because  of  its  strength 
and  shock-resisting  powers  Sitka  spruce  is  used  for 
airplane  work ;  while  in  the  manufacture  of  furniture 
and  pianos  the  wood  selected  is  usually  such  as  will 
approximately  match  the  texture  of  the  veneer  or 
crossbanding  with  which  it  is  to  be  united;  although 
quite  frequently  cost  is  the  prime  factor  in  determin- 
ing the  kind  of  wood  used  for  this  purpose.  But  less 
depends  on  the  variety  of  wood  than  on  its  preparation 
for  the  work  in  hand. 

When  we  say  that  wood  for  core  stock  should  be 
sound  we  mean  free  from  checks  of  various  kinds.  CORE  ST 
There  is  a  great  deal  of  wormy  chestnut  used  for  this  SHOULD  E] 
purpose,  and  to  this  there  is  no  serious  objection  un- 
less  it  is  so  badly  eaten  as  to  destroy  the  surface  for 
the  glue ;  and  this  is  hardly  conceivable. 

Only  one  variety  of  wood  should  be  used  in  each 


110 


MODERN  GLUES   AND  GLUE  TESTING 


CORESTOCK 
SHOULD  BE 
DRIED 


CROSSBANDIXG 


FACE    VENEER 
IS    THIN 


core.  If  two  kinds  of  wood  are  glued  together  in  one 
core,  say,  basswood  and  birch,  there  is  sure  to  be 
trouble  which  may  not  show  itself  until  after  the  goods 
are  finished.  The  swelling  of  these  two  woods  as  a  re- 
sult of  the  action  of  the  moisture  from  the  glue  will 
not  be  in  unison;  neither  will  the  shrinking  be  uni- 
form ;  and  an  uneven  surface  will  result  in  consequence. 

After  the  core  stock  has  been  glued  up  it  should  be 
sent  to  the  drying  room  in  order  that  the  joints,  which 
have  swollen  from  the  action  of  the  water  in  the  glue, 
may  shrink  back  to  their  normal  position.  If  they  are 
not  allowed  to  dry  out  properly  before  being  planed 
there  will  be  more  than  the  proper  amount  of  fiber  re- 
moved from  the  swollen  joint,  with  the  result  that 
when  the  joint  has  dried  out  it  will  have  shrunken  be- 
low the  level  of  the  surrounding  wood;  and  the 
depression  thus  made  will  show  after  the  stock  is  fin- 
ished, unless  a  very  heavy  crossband  has  been  used. 

For  the  better  grade  of  work  core  stock  is  always 
crossbanded.  This  crossband  consists  of  a  sheet  of 
wood  glued  on  each  side  of  the  core,  with  the  grain  of 
the  one  running  crosswise  of  the  grain  of  the  other; 
the  object  being  to  reinforce  it  to  prevent  checking, 
twisting  or  warping.  It  is  the  practice  in  some  shops 
to  lay  this  crossbanding  at  the  same  time  that  the  face 
veneer  is  laid ;  but  this  plan  is  not  here  recommended, 
nor  is  it  followed  in  the  best  shops.  The  plan  adopted 
by  those  who  have  the  best  quality  of  work  in  view  is  to 
lay  the  crossbanding  by  itself  and,  after  taking  from 
the  press,  pile  it  away  in  the  drying  room  with  strips 
between  each  piece  to  dry  out  before  laying  the  face 
veneer. 

Laying  the  crossbanding  in  advance  of  the  face 
veneer  has  several  distinct  advantages  over  the  laying 
of  both  at  the  one  time;  chief  of  which  is  the  better 
opportunity  it  affords  of  properly  preparing  the  sur- 
face for  the  face  veneer.  Fine  face  veneer  is  usually 
cut  very  thin,  and  any  unevennes  in  the  surface  to 
which  it  is  glued  will  be  reffected  through  it  after  the 
stock  is  finished,  and  will  detract  considerably  from 
the  quality  of  the  goods  as  well  as  add  to  the  cost  01 


PREPARATION  OF  CORE  STOCK 111 

finishing.  Crossbanding,  on  the  other  hand,  is  usually 
cut  much  heavier  than  veneer  intended  for  face  work, 
and  is  rotary  cut ;  that  is,  it  is  sliced,  or  peeled  off  the 
outside  of  the  log  as  the  latter  is  revolving  in  a  lathe. 
The  method  of  cutting  crossbanding  makes  it  difficult 
to  get  a  surface  sufficiently  smooth  for  fine  face  veneer 
without  some  cleaning  up;  and  this  cleaning  up  can 
best  be  done  after  the  crossbanding  has  been  fastened 
to  the  core. 

Allow  the  crossbanded  cere  to  remain  in  the  drying 
room  a  sufficient  length  of  time  to  become  properly  dry 
before  doing  anything  toward  cleaning  it  up ;  other-  ALLOW  THE 
wise  there  is  danger  of  weakening  the  glue-joint.  The  CROSSBANDED 
length  of  time  required  for  this  will  depend  on  the  c< 
capacity  of  the  drying  room;   but  in  a  room  such  as 
that  described  elsewhere  in  this  book,  from  three  to 
four  days  will  be  sufficient  to  eliminate  all  danger  of 
the  cleaning-up  process  affecting  the  glue  joint;  and 
render  it  sufficiently  dry  to  receive  the  face  veneer. 

This  cleaning-up  is  usually  done  by  putting  the 
stock  through  the  sander.  If  the  surface  is  in  pretty 
bad  shape,  use  two  or  more  drums,  with  coarse  paper 
on  each ;  no  fine  paper  being  used  for  this  operation.  It 
is  better  to  use  more  than  one  drum  for  cleaning  up, 
taking  shallow  cuts,  rather  than  one  drum  and  a  deep 
cut,  as  the  shallow  cuts  are  less  apt  to  affect  the  glue  by 
heating. 

It  is  very  important  to  have  the  crossbanding 
thoroughly  dry  before  it  is  laid.  There  are  some  who 
have  the  idea  that,  while  it  may  be  important  to  have 
the  face  veneer  dry,  the  condition  of  the  crossbanding  DRY 
is  not  a  matter  for  any  concern.  These  people  have 
their  troubles  in  consequence  of  their  neglect  in  this 
connection;  but  they  ascribe  the  cause  to  something 
else,  and  consequently  they  never  find  it,  and,  there- 
fore, do  not  remedy  it.  The  writer  has  seen  face  veneer 
broken  across  the  grain  in  consequence  of  being  laid  on 
crossbanding  which  has  not  been  properly  dried  before 
it  is  laid.  It  was  %-in.  crossbanding  and  had  checked 
in  the  process  of  drying  after  the  face  had  been  laid; 
and  at  the  point  of  these  checks  it  had  exerted  sufficient 


112 


MODERN  GLUES  AND  GLUE  TESTING 


DO  NOT 

MIX 

STOCK 


RIGHT  AND 
WRONG  SIDES 
OF  CROSS- 
BANDING 


RIGHT 

SIDE 

OUT 


force  to  rupture  the  face  veneer  above. 

What  we  have  said  about  the  importance  of  using 
only  one  variety  of  wood  in  a  core  applies  with  equal, 
if  not  greater,  force,  to  the  use  of  crossbanding ;  for 
the  nearer  our  work  brings  us  to  the  point  where  the 
face  veneer  is  to  be  laid,  the  more  the  necessity  for 
care.  If  one  has  a  lot  of  odds  and  ends  of  stock  of  vari- 
ous woods  that  he  wishes  to  use  up,  it  may  be  done  by 
sorting  the  lot  over  and  separating  each  kind  of  wood ; 
and  if  there  is  a  difference  in  thickness,  separating 
these,  too.  These  should  then  be  dried  and  cut  to  re- 
quired size,  then  taped  ready  for  use. 

There  is  always  a  right  and  wrong  side  to  rotary 
cut  stock;  and  the  thicker  the  stock,  the  more  pro- 
nounced is  this  distinction.  The  right  side  of  the  -stock 
is  that  which  was  on  the  outside  of  the  log  during  the 
process  of  cutting;  and  the  wrong  side  is  that  which 
was  the  inside  of  the  sheet  as  it  was  peeled  off  the  log. 
To  illustrate.  Take  a  long,  narrow  piece  of  paper  and 
bend  it  in  a  circle.  The  outer  side  of  this  circle  of  paper 
corresponds  to  the  right  side  of  the  crossbanding,  and 
the  inner  side  to  the  wrong  side  as  it  leaves  the  log. 
Now  straighten  the  paper  out  and  note  closely  in  your 
mind  what  follows.  Imagine  the  paper  to  be  %-in. 
more  or  less  thick,  and  see  the  strain  there  is  on  the 
inside  as  we  straighten  it  out.  The  strain  is  more  than 
the  fibers  can  withstand ;  and  they  break  and  separate. 
This  side  with  the  ruptured  grain  and  fiber  is  the 
wrong  side  of  the  stock. 

The  crossbanding  should  always  be  laid  with  the 
right  side  out — the  wrong  side  being  as  far  from  the 
face  veneer  as  possible.  The  right  side  is  much  more 
easily  cleaned  up ;  and  what  is  more,  if  the  wrong  side 
were  left  up,  the  ruptured  fibers  and  resultant  scales 
would  be  so  affected  by  moisture  from  the  glue  and 
subsequent  atmospheric  changes  that  they  would  im- 
part a  corrugated  appearance  to  the  face  veneer. 

The  right  side  of  crossbanding  is  the  side  to  be 
taped,  so  that  the  tape  will  be  removed  when  cleaning 
up  for  the  face  veneer.  But  this  applies  only  to  cross- 
banding  that  is  laid  in  advance  of  the  face  veneer.  If 


PREPARATION  OF  CORE  STOCK 113 

the  crossbanding  and  face  veneer  are  to  be  laid  at  the 
one  time  the  wrong  side  of  the  stock  is  the  side  which, 
in  this  case,  should  be  taped,  in  order  that  it  may  be 
laid  next  to  the  core  and  as  far  from  the  face  veneer  as 
possible.  The  joint  between  the  tape  and  the  wood  is 
not  as  firm  and  strong  as  a  glue  joint  between  two 
pieces  of  wood  made  under  pressure.  There  is  always 
danger  of  the  tape  coming  loose — hence  the  reason 
for  having  it  laid  as  far  as  possible  from  the  face 
veneer. 

As  before  intimated,  crossbanding  is  cut  in  various 
thicknesses ;  the  thickness  to  be  used  to  be  determined 
by  the  nature  of  the  work  in  hand.  Crossbanding  is 
done  to  add  strength — to  reinforce  the  thing  cross- 
banded;  and  unless  the  crossbanding  is  of  a  suitable 
thickness  to  match  the  core  it  will  be  a  source  of  weak- 
ness and  not  of  strength. 

If  one  is  making  thin  panel  stock  to  be  made  five- 
ply,  in  the  very  nature  of  things  everything  must  be 
thin — probably  Va-in.  core  with  1/20-in.  crossbanding 
and  1/30-in.  face.  But  if  one  is  making  a  heavy  buffet 
top  and  crossbanded  it  with  1/20-in.  stock  he  would 
very  likely  be  building  into  it  trouble  for  the  future. 
Such  thin  crossbanding  would  not  be  a  source  of  THICKNESS 
strength  to  a  heavy  top  that  needed  to  be  reinforced ;  OF  THE 
and  if  not  a  source  of  strength,  then  it  becomes  a  dan-  CORE  STOCK 
gerous  source  of  weakness.  Should  such  a  core  have  a 
tendency  to  warp,  such  a  thin  crossbanding  would  be 
more  likely  to  break  under  the  strain  imposed  than  to 
offer  any  effective  resistance ;  and  if  this  happened,  the 
last  state  of  the  top  would  be  worse  than  the  first. 
Nothing  less  than  i/s-in.  stock  should  be  used  for  cross- 
banding  l^-in.  core;  decreasing  or  increasing  in 
thickness  as  the  requirements  of  the  core  demand. 


CHAPTER  XXVII. 

PREPARING  GLUE  FOR  USE. 

THE  task  of  preparing  the  glue  required  for  the 
day's  work  should  never  be  entrusted  to  a  novice, 
but  to  a  person  of  high  intelligence  and  long 
experience.  Much  depends  on  how  this  work  is  done — 
a  mistake  at  this  end  of  the  line  may  prove  disastrous 
to  the  whole  output  of  the  day. 

While  a  person  of  experience  is  preferred  in  the 
preparation  of  glue  for  use,  any  man  of  good  intelli- 
gence with  experience  in  its  use  can  soon  grasp  the 
essential  points  and  become  proficient  at  the  work. 
But  it  cannot  be  done  in  an  hour,  nor  in  a  day,  and  for 
this  reason  every  glue  room  should  have  an  understudy 
who  is  qualified  to  take  the  place  of  the  head  glue  mixer 
in  the  event  of  the  latter  being  off  duty. 

There  is  a  difference  of  opinion  regarding  the  ques- 
tion of  soaking  glue  in  cold  water  before  heating  it  for 
use.  Our  modern  glue-mixers  have  made  it  possible  to 
reduce  glue  to  the  liquid  state  in  a  comparatively  short 
time  without  previous  soaking;  at  the  same  time  the 
writer  favors  soaking  first  where  this  can  be  done 
without  deterioration  of  the  glue,  as  it  is  not  good  for 
the  glue  while  in  the  dry  state  to  be  plunged  into  hot 
water,  or  even  into  a  hot  glue  solution.  But  if  the  glue 
is  put  into  the  dissolver  with  cold,  or  even  lukewarm 
water,  and  the  temperature  of  the  whole  raised  gradu- 
ally, no  injurious  effects  will  result,  and  previous  soak- 
ing is,  therefore,  unnecessary. 

Much  glue  is  injured  in  the  process  of  soaking, 
especially  in  hot  weather.   It  is  put  to  soak  too  far  in 
advance  of  requirements  the  process  of  decomposition  GLUE  IS 
sets  in  before  it  reaches  the  heater.  If  the  glue  can  be  INJURED 
kept  at  a  low  temperature  while  soaking,  no  bad  effects  IN*  SOAKING 
will  result  from  soaking  over  night,  or  even  a  few 
hours  longer.   If  one  has  more  glue  soaking  than  will 
be  required  for  the  first  three  or  four  hours'  work  it 
would  be  much  better  to  leave  it  in  the  cold  soak  than  to 


116 


MODERN  GLUES  AND  GLUE  TESTING 


DO  NOT 
MIX  OLD 
AND  NEW 
BATCHES 


put  it  in  the  hot  heater,  which  would  hasten  the  process 
of  decomposition.  Glue  that  is  kept  in  the  soak  may  be 
added  to  the  heater  at  intervals  as  required;  but  it 
would  be  better  to  always  empty  the  heater  before  add- 
ing fresh  glue.  The  reason  for  this  is :  Heat  deterior- 
ates glue,  and  the  process  of  deterioration  begins  soon 
after  a  certain  temperature  has  been  reached.  The 
change  is  very  slight  at  first,  nevertheless  there  is  a 
change ;  and  if  we  add  fresh  glue  with  some  of  the  old 
remaining,  the  deteriorating  effect  of  the  heat  on  the 
old  glue  is  increasing  until,  by  the  end  of  the  day,  that 
which  remains  of  the  early  morning  lot  has  decreased 
in  strength  probably  50  per  cent.  I  do  not  mean  that  all 
the  glue  in  the  heater  has  deteriorated  to  that  extent — 
only  the  original  lot,  which,  being  mixed  with  fresh 


FIG.  18 


PREPARING   GLUE   FOR   USE  117 

glue,  has  saved  itself  from  being  rendered  practically 
useless  for  permanent  work;  but  saved  itself  at  the 
expense  of  the  glue  that  was  added  from  time  to  time 
by  distributing  itself  throughout  the  whole. 

There  is  always  an  advantage  in  having  glue  soaked 
ready  for  the  heater,  as,  in  case  of  emergency,  one  can 
prepare  it  in  a  very  short  time  and  more  easily  regu- 
late the  supply  for  the  day's  requirements.  And  where 
one  must  soak  the  glue,  some  method  for  keeping  it 
cool  and  prevent  a  lessening  of  its  quality  should  be 
adopted.  For  this  purpose  a  cupboard  with  shelves 
(Figure  18)  on  each  of  which  is  placed  a  coil  of  water- 
pipes  with  cold  water  running  through  them  and  on 
which  the  pans  of  soaking  glue  are  placed,  will  keep 
the  glue  at  a  sufficiently  low  temperature  to  prevent 
injury  within  a  reasonable  time.  The  water  which 
runs  through  these  pipes  need  not  be  wasted,  as  it  can 
be  turned  into  the  reservoir  and  saved  for  boiler 
purposes. 

The  idea  that  glue  must  be  "cooked"  before  it  is  "COOKING"  is 
ready  for  use  has  long  since  been  exploded.  Time  was  UNNECESSARY 
when  men  thought  that  glue  would  not  hold  unless  it 
was  heated  to  the  boiling  point  and  kept  there  for 
some  time — all  the  way  from  one  to  three  hours.  And 
this  was  done,  all  unconscious  of  the  fact  that  each 
minute  of  sustained  heat  was  eating  at  the  very  life  of 
the  glue  and  lessening  its  adhesive  qualities.  In  those 
days  men  talked  of  glue  "cookers ;"  but  with  the  pass- 
ing  of  the  cooking  idea  there  passed  away  also  the 
words  which  gave  the  idea  expression;  and  in  their 
place  have  come  the  words  "heater"  and  "dissolver," 
which  signify  just  what  they  are  expected  to  do. 

While  one  must  not  cook  animal  glue  in  preparing 
it  for  use,  it  must  not  be  used  cold  or  at  too  low  a  tem- 
perature. There  is  a  tendency  on  the  part  of  some  peo- 
ple to  rush  to  the  other  extreme  when  the  danger  of  A  THERMOME- 
one  extreme  is  pointed  out  to  them.    Some  have  rea-  TER  is 
soned  that  if  heat  injures  glue,  then  the  proper  way  to  NECESSARY 
use  it  is  cold ;  and  they  have  tried  to  do  this,  but  with 
disastrous  results.  The  proper  temperature  at  which  to 
use  glue  to  obtain  best  results  is  140  to  150  degrees 


118 


MODERN  GLUES  AND  GLUE  TESTING 


CLEANING 
VAT 


KEEP  THE 
GLUE  ROOM 
CLEAN 


Fahrenheit :  and  as  soon  as  it  reaches  this  temperature 
it  is  ready  for  use.  Every  glue  heater  should  be 
equipped  with  a  thermometer  for  registering  the  tem- 
perature of  the  solution.  No  matter  what  else  one  has 
or  has  not,  a  thermometer  should  be  considered  an  in- 
dispensable part  of  the  glue  room  equipment. 

As  a  preliminary  to  each  day's  operations  the 
greatest  care  should  be  exercised  the  evening  before  in 
cleaning  up  all  the  glue  room  utensils.  If  these  are  not 
kept  clean,  tire  stale  glue  adhering  to  them  will  become 
mixed  with  the  day's  preparation  and  set  up  a  deterio- 
rating influence.  For  this  purpose  a  vat,  of  the 
required  size,  filled  with  water  into  which  the  utensils 
may  be  placed  to  soak  away  the  old  glue,  will  be  of 
great  advantage;  then  in  the  morning  they  may  be 
rinsed  clean  with  clear  water,  which  will  take  but  a 
few  moments.  The  vat  should  have  a  drain  pipe  at  the 
bottom  with  a  valve  to  facilitate  cleaning,  and  should 
be  emptied  and  refilled  each  day,  otherwise  it  will  soon 
become  foul  and  offensive. 

Every  glue  room  operator  should  contribute  his 
share  toward  making  working  conditions  as  pleasant 
as  possible.  The  glue  room  may  be  made  a  pleasant 
place  in  which  to  work  if  ordinary  care  is  exercised, 
but  if  neglected  it  is  liable  to  reach  the  opposite  ex- 
treme. If  the  floors,  benches  and  machines  are  kept 
clean  from  the  start  they  will  give  very  little  trouble, 
as  but  little  time  is  required  to  keep  them  clean  if  they 
are  cleaned  daily.  But  if  they  are  allowed  to  go  on  for 
days,  and  sometimes  weeks  and  months,  daily  accumu- 
lating fresh  coats  of  glue,  the  condition  will  soon  be- 
come such  that  no  man  with  any  regard  for  his  per- 
sonal comfort  or  any  knowledge  of  the  rules  of  health 
would  remain  in  the  room  longer  than  would  be  abso- 
lutely necessary.  The  benches  should  be  scraped  and 
the  floor  washed  with  hot  water.  A  few  minutes  the 
last  thing  before  leaving  at  night  will  make  everything 
clean  and  sweet  and  put  the  room  in  such  shape  that 
one  will  not  dread  to  enter  it  in  the  morning. 

The  careful  and  economical  glue  mixer  will  keep  in 
touch  with  the  progress  of  the  work  in  the  gluing-up 


PREPARING   GLUE   FOR   USE 


119 


department  in  order  to  know  how  much  glue  to  keep  in 
course  of  preparation,  and  not  have  any  left  over  at  the 
end  of  the  day.  In  warm  weather  glue  that  has  been 
left  over  from  the  day  before  will  seldom  be  fit  for  use 
and  is  usually  thrown  away.  There  is  a  great  quantity 
of  glue  wasted  in  this  way,  and  it  ought  not  to  be. 
With  glue  soaked  ready  for  heating,  it  would  be  a  very 
small  matter  to  prepare  an  additional  lot,  should  the 
day's  supply  run  out  before  the  day  is  done,  and  there 
need  be  no  hold-up  of  the  work  or  time  wasted.  In  view 
of  this  there  is  no  excuse  for  having  a  quantity  left 
over  to  be  thrown  away  and  wasted. 

Decomposition  of  glue  is  frequently  hastened  by  the  USE  PU8E 
water  with  which  it  is  mixed.    If  this  water  contains  WATER 
organic  impurities,  the  process   of  decay  will   com- 
mence as  soon  as  the  water  and  glue  come  together. 
The  value  of  glue  may  easily  be  reduced  one-half  by  the 
use  of  impure  water. 

There  are  many  things  to  be  found  in  water  which 
will  injure  glue.  Water  drawn  from  extremely  deep  RAIN  WATER 
wells,  as  well  as  river  water  which  flows  over  a  lime-  1S  GOOD 
stone  bed,  will  frequently  contain  a  sufficient  quantity 
of  lime  or  iron  or  other  chemicals  to  seriously  injure 
the  glue.  Some  concerns  that  use  a  large  quantity  of 
glue  have  found  the  ordinary  sources  of  water  such  a 
menace  to  their  glue  that  they  adopted  the  use  of  dis- 
tilled water  for  mixing  purposes.  Water  from  the 
boiler,  or  water  into  which  steam  from  the  boiler  has 
been  condensed  ought  not  to  be  used  for  mixing  glue. 
Most  boiler  compounds  are  injurious  to  glue,  and  con- 
densed steam  from  the  engine  is  most  certain  to  con- 
tain a  quantity  of  grease  or  oil.  Where  it  can  be  ob- 
tained, clean,  fresh  rain  water  should  be  used  for  mix- 
ing glue;  or  if  this  is  not  obtainable,  some  means 
should  be  adopted  for  purifying  the  water,  either  by 
filtering  or  distillation. 

Water  containing  an  excess  of  lime  may  be  purified 
by  adding  one-half  pound  of  ordinary  washing  soda  to 
a  thousand  gallons  of  the  water.    The  effect  of  the 
chemical  action  produced  by  the  soda  will  be  the  pre-  S(  DA  WILL 
cipitation  of  the  impurities  to  the  bottom  of  the  ves-  P 


120 


MODERN  GLUES  AND  GLUE  TESTING 


PREPARATION1 
OF  GLUE 


GRAIN   OF 

THE 

WOOD 


sel.  But  one  must  be  careful  and  not  use  the  soda  in  a 
larger  proportion  than  the  above,  as  washing  soda  is 
an  alkali,  which,  in  certain  proportions,  would  be  in- 
jurious to  the  glue,  and  the  last  state  would  then  be  no 
better  than  the  first. 

It  is  very  difficult,  except  in  the  open  country,  to 
obtain  rain  water  that  is  not  impregnated  writh  impuri- 
ties, such  as  soot,  etc.,  gathered  from  the  air  in  its  de- 
scent to  earth.  Such  impurities  may  be  removed  by 
filtering  the  water  through  charcoal.  Place  several  lay- 
ers of  burlap  in  the  bottom  of  a  barrel  or  tank,  over 
which  place  a  foot  or  so  of  powdered  charcoal,  and  let 
the  water  filter  through  this.  The  tank  should  be 
cleaned  out  at  intervals,  the  length  of  which  must  be 
determined  by  the  condition  and  quantity  of  water  to 
be  filtered. 

The  proper  preparation  of  glue  for  the  wood-work- 
ing plant  requires  considerable  knowledge;  especially 
is  this  so  in  the  preparation  of  glue  for  the  veneer 
room.  One  must  know  the  kind  of  glue  he  is  using,  also 
the  kind  of  wood  on  which  it  is  to  be  used.  Different 
glues  require  a  different  percentage  of  water  in  their 
preparation,  and  different  woods  require  a  glue  solu- 
tion of  a  different  consistency.  Hard,  close-grained 
woods,  such  as  maple  and  birch,  do  not  require  as 
heavy  a  glue  solution  as  basswood  or  poplar,  which, 
while  close-grained,  are  soft  and  absorbent  and  will 
imbibe  a  lot  of  glue ;  nor  yet  as  heavy  a  solution  as  oak, 
which,  while  hard,  is  very  porous  and  will  absorb  a 
large  quantity  also. 

Where  one  has  to  prepare  a  glue  solution  for  one 
kind  of  wood,  say,  a  hard  wood  or  a  soft  wood,  it  is  a 
comparatively  easy  matter ;  but  where  one  is  called  on 
to  prepare  a  solution  to  meet  the  requirements  of  two ; 
the  problem  is  perplexing,  as  one  cannot  have  a  thin 
and  a  thick  glue  both  in  the  one  solution.  But  the  glue 
room  is  sometimes  expected  to  do  more  than  its  share ; 
and  this  is  one  of  the  instances.  As  a  matter  of  fact, 
one  cannot  prepare  a  glue  solution  that  will  meet  the 
requirements  of  the  two  extremes  of  hard  and  soft 
woods  unless  these  two  woods  will  come  part  way  and 


PREPARING   GLUE   FOR  USE 


121 


partially  meet  the  requirements  of  the  glue.  This  diffi- 
culty is  probably  met  with  in  the  preparation  of  glue 
for  the  veneer  room  more  frequently  than  anywhere 
else. 

As  before  said,  where  two  kinds  of  woods  are  to  be 
glued  together,  both  glue  and  wood  must  go  part  way  A  PROBLEM 
to  meet  the  requirements  of  the  other.  Suppose  we  are  SOLVED 
laying  a  poplar  crossbanding  on  a  maple  core.  Here  is 
a  case  where  the  core  requires  a  thin  glue  and  the 
veneer  a  comparatively  heavy  glue.  In  a  case  of  this 
kind  we  will  have  to  prepare  the  glue  to  meet  the  re- 
quirements of  one  of  the  woods,  and  prepare  the  other 
wood  to  meet  the  requirements  of  the  glue.  In  this 
case  the  correct  plan  would  be  to  prepare  the  glue  to 
meet  the  needs  of  the  soft  veneer ;  and  prepare  the  hard 
marie  core  to  meet  the  glue.  This  can  be  done  by  pre- 
paring a  heavy  glue  solution  for  the  veneer  and  rais- 
ing the  fibers  of  the  hard  core  by  sanding  with  coarse 
paper. 

But  let  us  reverse  the  situation  and  bring  out  a  lot  USING  A 
of  hard  veneer  to  be  laid  on  whitewood  or  basswood  GLUE  SIZE 
cores.  For  obvious  reasons  we  cannot  machine  sand 
the  veneer  as  we  did  the  hard  core  in  the  other 
instance,  and  the  process  of  hand  sanding  is  too  slow 
and  expensive  to  be  considered;  so  we  will  have  to 
again  prepare  the  glue  to  meet  the  requirements  of  the 
veneer,  only  it  must  be  made  thin  this  time,  and  face 
the  problem  of  how  to  prepare  the  soft  core  to  meet  the 
requirements  of  the  glue.  The  problem  thus  presented 
is  solved  by  glue-sizing  the  soft  core  with  a  thin  glue 
solution ;  thus  sealing  up  the  pores  and  neutralizing  its 
absorbant  qualities.  This  glue-size  should  become 
quite  dry  before  the  gluing-up  process  begins. 

The  proportion  of  glue  and  water  to  be  used  in  pre- 
paring the  glue  solution  for  any  wood  is  determined  as 
much  by  the  kind  and  quality  of   the  glue  as  by  the 
wood  on  which  it  is  to  be  used — usually,  if  not  always, 
the  proportion  of  water  increasing  with  an  increase  in  THE  GLUE 
the  quality  of  the  glue.  And  in  the  preparation  of  glue  SHOULD  BE 
there  should  be  no  guesswork.    The  strength  of  the  WEIGHED 
glue  should  be  known  as  well  as  the  requirements  of 


122 MODERN  GLUES  AND  GLUE  TESTING 

the  wood  on  which  it  is  to  be  used ;  and  the  glue  should 
be  weighed  and  the  water  measured.  I  wish  to  empha- 
size the  importance  of  weighing  the  glue,  because  in 
the  minds  of  some,  it  is  so  much  easier  to  measure  glue 
than  it  is  to  weigh  it;  and  they  follow  the  course  of 
least  resistance.  But  a  bushel  of  glue  does  not  always 
weigh  the  same — that  is,  one  bushel  of  glue  may  weigh 
several  pounds  more  or  less  than  another  bushel  of 
even  the  same  grade  of  glue — the  weight  depending 
largely  on  the  condition  of  the  glue.  A  finely  ground 
glue  will  rest  more  compactly  in  the  measure  than 
would  be  the  case  with  coarse,  flake,  shell  or  cake  glue, 
and,  therefore,  weigh  more ;  the  weight  increasing 
with  the  fineness. 

After  one  has  ascertained  the  requirements  of  any 
given  wood,  as  well  as  the  proper  glue  solution  to  meet 
these  requirements,  he  should  make  a  memorandum  of 
the  facts  and  preserve  the  data  for  future  reference; 
as  it  is  not  safe  to  trust  to  memory  in  a  matter  of  such 
importance.  This  memorandum  should  contain  all  the 
known  facts  concerning  the  glue ;  including  the  result 
of  all  tests,  if  tests  of  a  specific  nature  have  been  made. 
The  great  range  in  the  quality  of  different  glues 
makes  it  inadvisable  to  frequently  change  the  make 
unless  one  has  a  well  equipped  laboratory  for  testing 
the  article.  Even  then  the  practice  is  a  questionable 
one  from  an  economical  standpoint.  When  one  has  a 
glue  made  by  a  reliable  concern  that  has  met  the 
requirements  of  the  past  there  should  be  some  greater 
BE  CAREFUL  reason  than  a  mere  desire  to  try  some  other  kind  be- 
IN  CHANGING  fore  &  change  is  made.  If  one  has  a  laboratory  for 
thoroughly  testing  glue  it  would  be  well  to  be  always  on 
the  lookout  for  something' better  and  cheaper;  and 
whether  a  proposition  to  change  glue  is  advisable  or 
not  can  be  ascertained  by  testing  a  sample.  But  where 
there  is  no  proper  equipment  for  testing  glue,  the  glue 
room  operator  is  placed  at  a  disadvantage  each  time  a 
change  is  made,  in  that  he  must  learn  his  glue  all  over 
again ;  and  perhaps  spoil  considerable  work  before  he 
understands  it. 


CHAPTER  XVIII. 

IDEAL  SURFACE  FOR  GLUING. 

E  fact  that  there  is  such  a  thing  as  an  ideal  sur- 
face for  gluing  or  one  that  is  more  likely  to  make 
a  permanent  job  than  another,  has  been  recog- 
nized as  far  back  as  the  time  when  all  woodworking 
was  done  by  hand ;  for  in  those  days  the  wood-worker 
had  his  toothing  plane  with  which  he  made  very  fine 
grooves  in  the  wood  for  the  purpose  of  removing  the 
smooth,  polished  surface  made  by  the  hand  plane  in  the  THE  GLUE 
process  of  cleaning  up  the  surface  preparatory  to  the  SURFACE 
gluing  and  laying  of  the  veneer.  Good  glue  will  retain 
its  hold  for  some  considerable  time  on  any  good,  clean 
surface;  but  where  one  desires  a  glue  joint  that  will 
be  permanent,  and  one  that  will  outlive  the  maker,  he 
should  give  special  care  to  the  preparation.  The  proper 
preparation  of  a  surface  for  gluing  is  a  comparatively 
easy  matter  today,  because  of  increased  facilities  for 
doing  the  work.  It  is  pretty  generally  recognized  and 
admitted  that  the  ideal  surface  is  one  that  is  perfectly 
level  and  on  which  the  fibers  of  the  wood  are  suffici- 
ently loose  to  allow  the  glue  to  penetrate  and  secure  a 
firm  hold ;  at  the  same  time  not  sufficiently  so  to  allow 
the  glue  to  accumulate  in  quantity  and  prevent  any 
surplus  squeezing  out. 

In  preparing  such  woods  as  maple  and  birch,  and 
other  hard,  close-grained  woods,  the  drum  sander,  with 
but  one  drum  fitted  with  coarse  paper,  will  prepare  a 

_._  .  -    .  11*  i  -TI  i  HARD  WOODS 

surface  which,  everything  else  being  equal,  will  make  a 
glue  joint  that  will  last  away  beyond  the  lifetime  of  the 
man  who  did  the  work. 

It  may  not  always  be  convenient  to  use  the  drum 
sander  for  the  purpose  of  preparing  corestock  for  glu- 
ing; then  the  scraping  machine  may  be  used  for  the 
purpose.  In  fact,  for  some  woods  the  scraper  is  prefer- 
able to  the  sander.  For  instance,  such  woods  as  oak  or 
chestnut,  which  have  hard  and  soft  places,  the  sander 
is  liable  to  press  deeper  into  the  soft  places  than  into 


324 


MODERN  GLUES  AND  GLUE  TESTING 


GLUE  SIZE 
END  GRAIN 


GLUING 

EDGES 

TOGETH1 


the  hard;  and  an  uneven  surface  will  be  the  result. 
With  the  scraper  it  is  different,  as  the  cut  will  be  uni- 
form over  the  hard  and  soft  places.  A  special  blade  for 
this  work  is  now  made  by  some  manufacturers  of 
scrapers. 

Difficulty  is  frequently  experienced  in  making  a 
glue  joint  on  end  wood,  or  in  gluing  the  grain  side  of 
one  piece  to  the  end  wood  of  another.  The  cause  of  the 
difficulty  is  usually  in  the  end  wood,  which  absorbs  all 
the  glue.  Or  in  cleaning  up  the  end  wood  it  may  be 
polished  too  smooth;  or  in  cutting,  the  saw  may  have 
burned  it  smooth  and  hard,  which  is  likely  to  be  the 
case  with  a  hard  wood  like  maple  and  birch  and  some- 
times even  walnut.  In  this  latter  case  the  remedy  is  to 
remove  the  hard  surface  with  sandpaper,  rubbing  suf- 
ficiently to  merely  break  the  polish. 

If  the  end  wood  is  open-grained  or  otherwise  of  an 
absorbing  nature  it  would  be  well  to  glue-size  it  to  seal 
up  the  pores,  using  a  thin  glue  for  the  purpose.  This  is 
advisable  on  such  woods  as  basswood  and  poplar  and 
even  oak. 

The  preparation  of  the  glue  joint  between  boards 
for  building  up  corestock,  or  for  other  purposes,  is 
equally  as  important  as  that  for  veneering.  Here,  as 
elsewhere,  to  insure  a  permanent  joint  the  surface 
should  not  be  smooth  and  hard.  A  good  glue  joint,  that 
is,  one  made  with  a  high  grade  glue  and  with  the  sur- 
face of  the  wood  in  an  ideal  condition,  should  never 
open  under  normal  conditions.  Of  course,  if  a  glue 
joint  becomes  soaked  with  water,  unless  it  is  a  water- 
proof glue,  it  will  open.  But  under  what  we  may  call 
the  average  condition  the  wood  will  break  before  the 
glue  will  give  way. 

In  addition  to  the  proper  preparation  of  the  surface 
the  edges  of  the  pieces  to  be  glued  should  not  be  made 
perfectly  straight,  but  should  be  made  slightly  hollow 
to  insure  permanency.  The  writer  was  once  consulted 
regarding  the  cause  of  open  joints  and  on  investigation 
found  that  the  joints  were  being  made  slightly  rounded 
— that  is,  the  boards  were  made  slightly  wider  in  the 
center  than  at  the  ends.  The  object  being  to  facilitate 


IDEAL  SURFACE  FOR  GLUING 125 

clamping  up,  as  only  one  clamp  on  each  end  of  a  four- 
foot  board  was  being  used;  the  argument  being  that 
there  was  sufficient  spring  in  the  center  of  the  rounded 
board  to  take  the  place  of  clamps. 

But  the  man  who  conceived  the  idea  of  gluing  up 
stock  in  this  manner  had  overlooked  a  very  important 
factor  in  determining  the  quality  of  the  joint,  and  that 
is,  the  spring  supplied  to  the  center  as  a  result  of  the  ACTg  BOTH 
rounded  edge  of  the  board  was  a  permanent  force,  and  WAY8 
one  which  operated  two  ways ;  for  while  it  gave  press- 
ure to  the  center  when  clamping  up,  it  was  forcing  the 
joint  apart  at  the  ends  when  the  clamps  were  removed. 
This  force,  together  with  the  fact  that  the  ends  of  a 
glue  joint  always  dry  out  more  rapidly  than  the  parts 
farther  in  and  which  creates  a  strain  on  the  ends  which 
dry  out  first,  was  sufficient  to  draw  the  joints  apart;  in 
some  instances  breaking  the  wood  in  the  immediate 
vicinity  of  the  joint. 

An  ideal  edge  for  gluing  up  is  one  that  is  slightly 
hollow  or  concave;  that  is,  when  the  two  edges  are 
placed  together  they  will  meet  at  the  ends  only,  gradu- 
ally and  slowly  separating  toward  the  center.  This 
requires  more  force  and  more  clamps  to  bring  the 
edges  together  than  is  the  case  with  the  rounded  edge ; 
and  although  the  spring  or  force  resulting  from  the  °°NCAVE 
concave  edges  is  a  permanent  one,  it  is  evenly  dis-  EDGE  Zl 
tributed  from  the  center  to  the  end,  and  is  so  located 
that  it  is  comparatively  harmless.  In  any  event,  the 
strain  is  in  the  center  and  far  away  from  the  ends, 
where  glue  joints  usually  open.  Not  only  that,  but  it 
is  a  positive  help  to  the  ends,  as  it  increases  the  pres- 
sure of  each  piece  toward  each  other  at  these  points 
instead  of  away  from  each  other,  which  tends  to 
permanency. 


CHAPTER  XIX. 
THE  COVERING  CAPACITY  OF  GLUE. 

EVERY  manufacturer,  regardless  of  line,  is  inter- 
ested in  the  covering  capacity  of  the  glue,  for  it 
is  this  point,  all  other  factors  considered,  that 
determines  the  cost  of  the  glue.   We  know  that  high- 
grade  glues  will  take  more  water  than  low  grade;  on 
the  other  hand,  high-grade  glues  would  prove  too  ex- 
pensive for  certain  purposes,  as,  for  instance  in  the  HIGH  GRADE 
manufacture  of  paper  boxes.    Again,  one  would  not  GLUES  SET 
use  high-grade  glues  in  veneering,  regardless  of  cost,  T°°  QUICKLY 
because  they  set  too  quickly.  We  know  that  liquids  hav-  FOR  VENEERING 
ing  the  same   specific   gravity  will   cover   the   same 
amount  of  surface.    Also,  as  has  been  previously  ex- 
plained that  glues  can  be  prepared  to  give  the  same 
viscosity   tests    (varying   proportions   of  water   and 
glue)  ,  hence,  the  liquids  being  the  same,  they  will  cover 
the  same  amount  of  square  surface. 

The  following  table  was  published  in  Glue,  June 
number,  1911. 

COVERING    CAPACITY    PER    1    POUND    DRY    GLUE    OF 

STANDARD  AMERICAN  GLUE  GRADES  (BASED 

ON  PETER  COOPER  GRADES): 

Yield  of  Liquid  Glue  Covering  in 

Glue  Grade.  per  1  Ib.  Dry  Square  feet. 

A  Extra   ........................  3.65  79 

1  Extra  .........  _  .............  3.45  75 

1    .......................  _  ...........  3.34  72 

IX  ..................................  3.08  67  COVERING 


-  2.94  64  CAPACITY 


1%    .......................  _  .......  2.82  61 

1%    ................................  2.68  58 

1%    ................................  2.55  55 

1%    ................................  2.43  53 

1%    ...................  -  ...........  2.31  50 

2    ....................................  2.19  47 

It  is  to  be  regretted  that  glue  prices  have  been  so 
uncertain,  and  will  likely  be  so  for  some  time  to  come 
that  we  cannot  cite  a  correct  example  as  to  possible 
savings,  however,  one  can  easily  figure  differences  in 


128 


MODERN   GLUES   AND  GLUE   TESTING 


DETERMINE 
THE    SPREAD 
COSTS 


MUCH    GLUE 
IS    WASTED 


the  spread  costs  from  the  figures  given  in  the  table. 
For  example,  A  Extra  will  with  1  Ib.  dry  glue  cover 
nearly  70  per  cent  more  surface  than  can  be  covered 
with  1  Ib.  dry  glue  of  the  grade  No.  2. 

The  writer  has  always  advised  his  clients  to  deter- 
mine the  cost  of  spread  from  the  cost  records.  The 
cost  scheme  should  show  the  number  of  square  feet 
covered  in  your  veneering,  joint,  or  to  whatever  line  or 
use  your  glue  has  been  applied.  You  know  or  should 
know  the  amount  of  glue  used,  and  this  will  give  the 
spread  cost.  Having  established  a  fairly  accurate 
amount,  use  this  glue  as  a  standard  in  future  spread 
tests  or  comparisons.  This  can  be  done  in  a  fairly  safe 
measure  by  comparing  viscosities. 

Someone  may  ask  the  question,  "Why  not  deter- 
mine the  glue  spread  from  laboratory  tests,  dissolving 
a  certain  quantity  of  glue  and  determining  the  surface 
covered  ?"  My  answer  is,  we  may  select  the  finest  and 
most  economical  glue  that  money  can  buy,  but  unless 
the  gluing  department  is  right  and  the  men  apply  and 
use  glue  correctly  our  spread  test  would  avail  us  noth- 
ing. Your  records  should  show  what  your  glue  costs 
are,  and  this  is  the  real  check  on  your  gluing  depart- 
ment. We  will  find  some  glue  rooms  equipped  with  the 
old  style  glue  pots  and  the  glue  applied  with  a  brush. 
We  will  find  other  modern  rooms  employing  the  latest 
types  of  glue-spreaders  and  find  they  cover  a  greater 
surface  than  the  men  daubbing  the  stock  and  likely 
wasting  from  ten  to  fifty  per  cent.  If  the  surface  of  the 
stock  covered  is  accounted  for,  the  glue  buyer  will 
know  that  something  is  radically  wrong.  Yes,  it  is  well 
to  get  a  line  on  your  spreading  by  testing,  but  in  the 
name  of  common  sense  do  not  depend  upon  these  tests. 

Suppose  you  buy  a  glue  worth,  say,  thirty  cents.  It 
passes  the  required  tests  and  is  a  pure  hide  product. 
The  men  in  your  glue  room,  however,  abuse  this  prod- 
uct by  overheating  so  that  when  actually  used  it  is 
worth  but  twenty-five  cents.  What  good  was  derived 
from  your  tests?  Why  not  buy  the  twenty-five  cent 
product  in  the  first  place  and  save  the  five  cents  that 
you  are  actually  wasting?  Therefore,  our  tests  and  the 


THE  COVERING  CAPACITY  OF  GLUE 129 

actual  final  result  must  be  considered.  When  you  know 
beyond  the  shadow  of  a  doubt  that  your  glue  is  prop- 
erly used  and  you  are  getting  one  hundred  per  cent 
glue  room  efficiency  then  you  can  apply  the  informa-  PER  CENT 
tion  given  regarding  the  spread  of  glue,  but  until  this  EFFICIENCY? 
degree  of  efficiency  has  been  attained,  your  assumed 
spread  cost  is  unreliable  and  cannot  be  depended  upon. 


130 


MODERN  GLUES  AND  GLUE  TESTING 


FIG.    19 


CHAPTER  XX. 
GLUE  ROOM  EQUIPMENT. 

COMING  to  the  practical  end  of  the  use  of  glue,  we 
would  say  that  in  this  day  of  rapid  processes  one 
must  have  a  modern,  up-to-date  equipment  in 
order  to  obtain  best  results.  It  is  true  that  some  very 
fine  work  was  done  in  the  olden  times  when  the  glue  MODERN 
pot  and  brush,  and  the  clamps  or  hand  press  comprised  GLUE  ROOM 
the  entire  glue  room  equipment,  and  the  glue  brush  APPLIANCES 
and  pot  had  to  compete  with  the  glue  brush  and  pot; 
and  the  clamps  and  hand  presses  had  to  compete  with 
the  clamps  and  hand  presses.  But  times  have  changed ; 
and  one  might  as  well  expect  the  old  stagecoach  to  com- 
pete today  with  the  modern  railroad  flyer,  or  the  old 
hand  sickle  to  compete  with  a  modern  harvester,  as  to 
expect  the  old  fashioned  glue  room  equipment  to  com- 
pete with  modern  appliances.  It  is  not  merely  a  ques- 
tion of  quality  of  work ;  but  in  these  times  of  keen  com- 
petition time  and  cost  are  important  items.  Nor  is  this 
all.  To  do  the  amount  of  work  demanded  of  the  modern 
glue  room  in  one  of  our  large  modern  factories — to  do 
this  amount  of  work  with  the  old  style  equipment 
would  require  almost  as  much  space  as  is  now  taken  up 
by  several  departments;  and  in  most  factories  floor 
space  is  an  important  matter. 

Glue  room  equipment  has  kept  pace  with  the  on- 
ward march  of  progress  in  other  spheres  of  activity — a 
steady  march  toward  greater  efficiency.  All  the 
changes  that  have  been  made  in  means  of  doing  the 
work  in  the  glue  room  have  been  for  the  purpose  of 
making  it  easier  to  do  the  work  in  less  time,  and  in- 
crease the  quality  where  possible.  The  checking  of 
veneer,  owing  to  the  presence  of  moisture  before  lay- 
ing, created  a  demand  for  the  redryer;  and  the  ten- 
dency of  dry  veneer  to  rapidly  absorb  moisture  from 
the  glue  created  a  demand  for  something  more  rapid 
than  the  hand  press,  and  the  hydraulic  press  came  into 
existence  (Figure  19).  The  same  may  be  said  of  the 


132 


MODERN  GLUES  AND  GLUE  TESTING 


other  modern  machines.  The  retaining  clamps  and  the 
overhead  carriers  came  in  response  to  a  demand  for 
economy  in  floor  space,  and  to  enable  the  one  power 
press  to  do  the  work  of  many.  The  glue  spreader  (Fig- 
ure 20)  responded  to  a  hurry-up  order  froni  the  power 
press  to  keep  it  busy,  as  men  could  not  spread  glue  fast 
enough  with  the  brush.  Then  the  modern  glue  dis- 
solver  came  to  prevent  these  rapid  machines  from 


FIG.  20 


GLUE   ROOM    EQUIPMENT 133 

standing  idle  while  glue  was  being  prepared  during 
the  early  part  of  the  day. 

It  is  not  enough  that  work  be  done  well — it  must  be 
done  in  the  shortest  possible  time  and  in  the  easiest 
possible  way ;  and  this  can  be  done  only  by  the  use  of 
the  best  equipment.    Every  manufacturer  is  anxious  WORK  MUST 
that  the  cost  of  operating  his  glue  room  be  reduced  to  BE  DONE  IN 
the  lowest  possible  point  consistent  with  good  work,  THE  SHORTEST 
and  the  result  of  our  observation  is  a  firm  conviction  POSSIBLE 
that  the  shops  with  the  lowest  operating  expense  are  T 
those  with  the  best  equipment.    The  first  cost  of  the 
plant  is  undoubtedly  greater,  but  the  difference  be- 
tween a  poor  and  a  good  equipment  is  soon  wiped  out 
by  the  saving  in  operating  expense  and  the  decrease  in 
the  cost  of  repairs. 

It  is  not  our  purpose  to  advocate  any  particular 
equipment,  as  every  factory  must  be  governed  by  its 
individual  needs ;  but  we  have  been  asked  so  often  re- 
garding the  best  kind  of  caul  for  use  in  the  veneer 
room  that  we  might  be  permitted  to  say  a  word  about 
this  part  of  the  equipment.  There  are  three  kinds  of 
cauls  in  general  use,  i.  e.,  wood,  metal  and  fiber  board. 
There  are  three  kinds  of  metal  cauls,  i.  e.,  iron,  zinc  and  KINDS  OF 
aluminum.  It  is  not  for  us  to  advocate  the  claims  of  CAULS 
any  of  these,  as  many  glue  room  operators  have  had 
success  with  all  of  them.  But  we  will  say  that  metal 
cauls  should  always  be  used  where  hot  glue  is  the  adhe- 
sive, because  they  will  absorb  and  retain  heat  more 
readily  than  wood  or  fiber ;  while  we  have  a  preference 
for  fiber  cauls  where  a  cold  glue  is  used,  because  they 
are  light  in  weight  and  easy  to  handle. 

We  have  been  frequently  asked  how  best  to  prevent 
glue  from  sticking  to  cauls.   In  the  case  of  fiber  cauls 
they  may  be  made  glue-proof  by  repeated  applications  To  PREVENT 
of  hot  parafine  oil  into  which  parafine  wax  has  been  GLUE  FROM 
melted  in  proportion  of  one  pound  of  wax  to  a  gallon  of  STICKING 
oil.  Heat  the  oil  as  hot  as  can  conveniently  be  done  and  T0  CAULS 
apply  it  until  the  caul  will  take  in  no  more.  The  idea  of 
the  wax  is  to  add  body  to  the  oil.  A  caul  thus  treated 
will  last  for  a   considerable  time  without  anything 
further  being  done  to  it ;  but  to  keep  it  in  prime  condi- 


134  MODERN  GLUES  AND  GLUE  TESTING 

tion  it  would  be  well  to  give  it  a  light  application  of  the 
oil  at  intervals,  the  length  of  which  will  depend  on  the 
frequency  with  which  the  caul  is  used. 

Metal  cauls  need  something  with  a  little  more  body 
than  oil.  Parafine  wax  has  been  used  by  some  with  fair 
success;  but  beeswax  is  better.  For  this  purpose  it  is 
not  necessary  to  use  the  genuine  beeswax,  as  there  is 
an  artificial  article  that  will  answer  the  purpose 
equally  well. 

With  all  cauls  care  should  be  taken  to  keep  them 
clean ;  and  care  should  be  taken  in  cleaning  them.  It  is 
not  a  good  plan  to  scrape  cauls  in  cleaning,  as  this  is 
liable  to  wear  them  thin  in  places,  resulting  in  a 
reduced  pressure  at  these  thin  points  when  in  the 
press,  which,  in  turn,  results  in  blisters  in  the  veneer. 
Metal  cauls  may  be  cleaned  with  steam  or  hot  water,  if 
one  has  a  vat  of  hot  water  to  put  them  in ;  or  they  may 
be  washed  off  with  a  rag  and  hot  water.  With  fiber 
cauls  there  is  less  liability  of  the  glue  adhering  to 
them,  owing  to  their  thorough  saturation  with  oil,  and 
if  any  does  adhere  it  can  easily  be  rubbed  off. 

But  cauls  should  always  be  examined  for  glue  be- 

OAULS  SHOULD   fore  being  used,  as  any  particles  which  may  be  present 

BE  EXAMINED      wju  ke  pressed  into  the  veneer,  leaving  dents  which 

will  likely  rise  and  give  no  end  of  trouble  during  the 

process  of  finishing. 


CHAPTER  XXL 

AN  IDEAL  GLUE  ROOM. 

TO  GET  best  results  in  the  use  of  glue,  whether  it 
be  in  gluing  up  solid  lumber  or  in  making 
veneered  stock,  one  must  have  a  proper  place  in 
which  to  do  the  work.  A  glue  room  located  in  a  base- 
ment with  a  seven  or  eight  foot  ceiling  is  not  conducive 
to  the  best  in  glued-up  work;  and  this  for  more  than 
one  reason.  Such  a  place  is  unfit  for  the  work ;  and  a 
man  capable  of  doing  good  work  under  proper  condi- 
tions can  easily  find  plenty  of  employment  in  more  con- 
genial surroundings,  and,  therefore,  is  not  likely  to 
remain  in  such  a  place. 

An  ideal  glue  room  for  doing  veneer  work  is  one 
located  on  the  ground  floor,  because  the  light  so  neces- 
sary for  matching  fine  veneers  is  better  here  than  it  is 
at  a  higher  altitude;  but  for  other  purposes  it  is  im- 
material whether  it  be  located  there  or  on  the  second 
floor.    If  located  on  the  ground  floor,  and  the  floor  is  SHOULD  SB 
cement  with  no  basement  beneath,  it  should  be  raised  LOCATED  ox 
to  prevent  dampness.  GROUND 

The  work  of  matching  veneers  and  preparing  the 
stock  for  gluing  should  not  be  done  in  the  glue  room 
proper;  but  should  be  done  in  a  room  immediately 
adjoining.  In  this  room  should  be  the  machines  for 
cutting  the  veneer  to  size  and  jointing  and  taping.  Also 
immediately  adjoining  the  glue  room  should  be  the 
drying  room ;  the  nature  and  importance  of  which  we 
will  consider  later  on. 

The  size  of  the  glue  room  must,  of  course,  depend 
on  the  volume  of  work  to  be  done,  but  in  laying  it  out 
it  would  be  well  to  make  provision  for  an  expansion  of 
business  in  order  to  avoid  hampering  the  work  through 
congestion. 

The  success  of  a  glue  room  depends  a  great  deal  on 
the  arrangement  of  the  equipment.  If  the  work  of  glu- 
ing up  the  solid  stock  is  done  in  the  same  room  with  the 


136 


MODERN  GLUES   AND  GLUE   TESTING 


LOCATION  OF 
THE  GLUE 
HEATERS 


SATISFACTORY 

HEATING 

ARRANGEMENT 


veneering,  the  appliances  for  doing  the  different  work 
should  be  so  separated  that  the  work  of  one  will  not  at 
any  time  interfere  with  the  work  of  the  other.  As  far 
as  possible  the  revolving  clamps  and  presses  for  the 
solid  lumber  work  should  be  located  at  the  side  of  the 
room  to  that  where  the  veneering  is  done,  leaving  the 
space  between  the  two  equipments  for  stock  in  process. 

The  glue  heaters  should  be  placed  in  one  corner  of 
the  room  with  the  glue  spreader  immediately  in  front 
of  them.  The  heaters  should  be  sufficiently  elevated  to 
allow  the  glue  to  flow  into  the  upper  and  lower  tanks 
of  the  spreader.  This  is  preferable  to  carrying  the  glue 
from  the  heater  to  the  spreader  in  buckets,  which  is 
liable  to  chill  the  glue  and  impair  its  quality.  The  glue 
should  be  run  from  the  heater  to  the  spreader  through 
a  detachable  pipe ;  and  this  should  be  taken  down  each 
night  and  cleaned  along  with  the  other  utensils. 

The  veneer  laying  bench  should  be  placed  in  close 
proximity  to  the  spreader  and  the  power  press  as  close 
to  this  as  is  practical,  to  avoid  unnecessary  carrying  of 
the  stock.  Near  the  heater  is  a  vat  into  which  the  uten- 
sils are  put  to  soak  to  facilitate  cleaning.  This  vat  is 
provided  with  a  drain-pipe  and  valve  to  allow  empty- 
ing every  day. 

The  heating  of  the  glue  room  is  an  important  mat- 
ter. The  forced  hot-air  system  is  not  here  recom- 
mended, as  there  is  too  much  danger  of  the  draft  com- 
ing in  direct  contact  with  freshly  glued  surfaces  and 
impairing  the  adhesive  quality  of  the  glue.  The  over- 
head steam  coil  is  not  recommended,  because  it  heats 
the  part  of  the  room  first  that  least  requires  it,  and  the 
part  toward  which  the  hot  air  will  move  in  any  event ; 
and  in  addition  to  this  it  is  hard  on  the  workmen.  The 
most  satisfactory  system  for  heating  will  be  found  to 
consist  of  one  or  more  coils  of  pipes  placed  along  the 
walls  about  one  foot  from  the  floor,  the  number  of 
pipes  to  the  coil  to  be  determined  by  the  space  to  be 
heated,  as  well  as  the  length  of  the  coils. 

A  well  conceived  glue  room  will  have  plenty  of  head 
room.  Where  animal  glue  is  used,  the  odors  are  not  of 
the  most  pleasant  sort  at  the  best  of  times,  but  are  par- 


AN   IDEAL  GLUE   ROOM 


137 


FIG.  21 


138 


MODERN  GLUES  AND  GLUE  TESTING 


A  FAN 

SHOULD    BE 
USED 


THE 

DRYING 

ROOM 


ticularly  nauseating  in  a  room  with  a  ceiling  so  low 
that  one  feels  as  though  he  were  in  the  midst  of  com- 
pressed offensiveness.  No  glue  room  should  be  less 
than  eighteen  feet  high,  and  then  a  fan  should  be  in- 
stalled for  carrying  off  the  foul  air.  This  fan  should  be 
located  near  the  ceiling  at  the  opposite  end  of  the  room 
to  the  one  where  the  spreader  is  in  operation,  and 
should  revolve  so  as  to  draw  the  air  out.  This  can  be 
done  without  disturbing  the  air  at  any  one  point  suf- 
ficiently to  create  a  draft.  Drawing  air  out  with  a  fan 
is  different  from  blowing  air  into  a  room  by  the  same 
means.  In  the  former  case  the  air  which  is  drawn  out 
of  the  room  is  taken  from  the  top  and  the  air  in  all 
parts  of  the  room  moves  upward  to  take  the  place  of 
that  which  is  being  carried  away.  The  movement  of 
the  air  is  so  slow  and  even  as  to  be  imperceptible,  there 
being  no  concentration  except  in  the  immediate  vicin- 
ity of  the  fan.  If  the  fan  be  reversed  and  the  air  blown 
into  the  room  it  will  be  forced  toward  a  given  point, 
creating  a  strong  draft. 

The  problem  of  how  to  admit  fresh  air  to  take  the 
place  of  that  drawn  away  by  the  fan  may  safely  be  left 
to  solve  itself.  No  room  is  airtight  and  the  weight  of 
the  air  outside  will  force  fresh  air  in  to  take  the  place 
of  that  which  escapes. 

The  drying  room  to  which  we  referred  a  short  time 
ago  should  be  considered  an  essential  part  of  every 
glue  room  equipment.  This  room  should  be  divided  into 
two  parts — one  part  for  warming  stock  before  going  in 
to  be  glued  up,  and  the  other  part  for  drying  stock 
after  it  has  been  glued  up.  The  importance  of  warm- 
ing stock  before  gluing,  and  of  drying  thoroughly  after 
gluing  and  before  working  up,  are  both  considered  in 
another  part  of  this  book.  While  we  advise  dividing 
this  room  into  two  compartments,  we  do  not  contend 
that  it  is  absolutely  necessary  to  do  so.  What  we  do 
claim  is  that  the  two  rooms  have  an  advantage  over 
the  one  room. 

Where  there  are  two  rooms,  one  room  can  be  used 
for  warming  the  stock  for  gluing  without  running  the 
risk  of  it  being  affected  by  the  moisture  that  is  being 


AN   IDEAL   GLUE   ROOM 139 

thrown  off  by  the  glued-up  stock ;  and  into  the  second 
room  the  glued-up  stock  may  be  run  to  finish  off  a  few 
hours  before  being  worked  up. 

Both  of  these  rooms  should  be  well  heated  and  ven- 
tilated. If  the  room  is  large  it  would  be  well  to  place  a 
coil  of  pipes  in  the  center  as  well  as  along  the  wall,  as 
this  will  increase  and  make  more  uniform  the  circula- 
tion of  the  air ;  and  circulation  is  essential  to  success  in  CIRCULATION 
a  drying  room.   The  heating  apparatus  should  have  a  OJ,AIR 
sufficient  radiation  to  keep   the  temperature  in  the  ESSENTIAL 
vicinity  of  110  degrees  Fahrenheit.  Ventilators  should 
be  placed  in  the  top  to  allow  the  vaporized  moisture  to 
escape.  In  a  several-story  building,  with  the  glue  room 
and  drying  room  on  the  ground  floor,  ventilators  are 
not  always  practical;  in  which  case  a  fan  should  be 
installed  to  carry  off  the  moist  air. 

The  foregoing  are  the  essential  features  of  an  ideal 
glue  room  connected  with  a  wood  working  plant.  But 
the  IDEAL  glue  room  would  be  a  building  one  story 
high,  with  light  from  above  as  well  as  from  all  sides. 
Such  a  room  would  have  to  stand  out  by  itself;  and 
while  it  would  be  "ideal"  from  its  own  viewpoint,  it 
would  be  inconvenient  from  the  viewpoint  of  the  other 
departments  of  the  factory. 


CHAPTER  XXII. 

EVOLUTION  OF  GLUE  ROOM  PRACTICE. 

AWAY  back  in  the  early  dawn  of  the  glue  and 
woodworking  industry  men  were  trying,  as 
they  are  today,  to  do  the  work  in  the  best  and 
easiest  way.  There  is  very  little  literature  extant 
which  would  throw  much  light  on  the  very  early  meth- 
ods of  gluing  up  wood  work,  but  the  contrast  between  A  BIT  OF 
the  methods  employed  half  a  century  ago  and  those  of  HISTORY 
the  present  day  is  sufficiently  great  to  be  startling  to 
the  old-time  cabinet  maker,  were  he  to  leave  his  Celes- 
tial abode  for  a  brief  visit  with  us  who  were  left  behind 
to  "carry  on"  after  he  had  gone.  In  the  early  days  the 
clamping-up  was  done  by  means  of  a  frame  not  unlike 
the  screw  clamp  in  use  today;  but  the  pressure  was 
exerted  by  means  of  wedges  driven  between  the  clamp 
and  the  edge  of  the  boards  to  be  pressed  together.  In 
those  days  the  glue  was  dissolved  in  a  kettle  on  a  stove 
and  brushes  were  the  only  means  of  applying  it  to  the 
wood.  A  wonderful  step  forward  was  made  when  the 
screw  clamp  was  brought  into  existence.  There  mat- 
ters rested  for  some  considerable  time;  or  until  the 
trade  of  "cabinet  maker"  became  divided  into  several 
different  branches.  In  the  old  days  the  cabinet  maker 
took  the  board  in  the  rough  from  the  yard  and  carried 
the  work  along,  planing,  jointing  and  gluing,  assembl- 
ing and  finishing  until  the  article  was  completed.  But 
when  the  furniture  and  kindred  industries  grew  to  be 
of  national  importance  they  outgrew  the  old  fashioned 
method  and  the  one  trade  of  cabinet  making  became 
many  trades;  hence  it  is  that  we  have  the  glue  room 
specialist  of  today.  With  the  advent  of  the  glue  room 
specialist  this  department  became  recognized  as  an 
important  branch  of  the  woodworking  industry,  and 
some  of  the  best  mechanical  brains  were  directed  to- 
ward improving  the  method  of  doing  the  work,  so  as 
to  improve  the  quality  and  lessen  the  cost. 

Then  the  time  came  when  the  work  of  the  glue  room 


142 


MODERN  GLUES  AND  GLUE  TESTING 


GREAT 
STRIDES 
HAVE    BEEN 
MADE 


MANY   PROB- 
LEMS   REMAIN 
TO  BE  SOLVED 


specialist  was  divided  and  some  followed  after  the  glu- 
ing-up  of  boards;  and  others  followed  the  gluing  of  a 
face  veneer  on  these  boards.  From  this  time  on  things 
moved  with  startling  rapidity,  so  much  so  that  a 
detailed  account  would  read  almost  like  a  fairy  tale.  It 
is  a  long  step  from  the  old  hand  plane  and  glue  brush 
to  the  modern  automatic  glue  jointer,  on  which  the 
lumber  is  jointed,  glued,  clamped  and  cut  to  size  in  one 
automatic  operation ;  and  yet  it  is  a  step  that  has  been 
taken  by  many  men  yet  able  to  do  a  good  day's  work. 
It  is  equally  far  from  the  old  glue  kettle  sitting  on  a 
stove  to  the  modern  steam  or  electrically  heated  dis- 
solver  with  its  thermometer  and  automatic  heat  con- 
troller to  prevent  overheating  and  spoiling,  and  its 
power  agitators  to  facilitate  solution  and  reduce  time 
and  labor  costs;  and  yet  many  who  read  this  have 
spanned  the  distance.  Measured  from  the  viewpoint  of 
accomplishment,  it  is  a  wonderful  stride  from  the  old 
glue  brush  and  bucket  to  the  modern  glue  spreader 
with  its  rolls  designed  to  spread  heavy  or  light,  to 
spread  on  one  side  or  both  sides  of  the  board,  as  the 
requirements  of  the  work  in  hand  may  demand.  The 
same  may  be  said  of  the  distance  between  the  flatirons 
used  in  rubbing  on  veneers  in  ancient  days  and  the 
clamps  and  clumsy  hand  presses  of  a  later  period:  or 
between  these  and  the  quick-acting  and  powerful  hy- 
draulic presses ;  and  from  the  old  rack  above  the  stove 
for  drying  veneers  preparatory  to  gluing  to  the  mod- 
ern redryer;  and  yet  many  who  will  read  this  have 
lived  to  see  it  all. 

All  these  things  have  tended  to  solve  the  problems 
of  the  glue  room ;  but  there  are  many  problems  belong- 
ing to  the  individual  glue  room  that  yet  remain  to  be 
solved.  Equipment  alone  cannot  solve  them.  The  same 
high  quality  brain  power  that  brought  these  machines 
into  being  must  guide  them  in  their  operations  if  they 
are  to  accomplish  all  they  were  designed  to  do.  At  one 
time  many  were  of  the  opinion  that  a  machine  was  a 
failure  if  a  man  lacking  in  mental  capacity  could  not 
keep  it  in  successful  operation.  But  the  fact  that  a 
machine,  no  matter  how  perfected,  is,  after  all,  but  a 


EVOLUTION  OF  GLUE  ROOM  PRACTICE 


143 


machine,  without  innert  animation  and  but  reflects  the 
intelligence  of  its  designer  and  builder  in  operating  it, 
is  now  becoming  more  generally  recognized. 

That  the  foregoing  contention  is  correct  is  borne 
out  by  the  experience  of  European  countries,  as  well  as 
by  the  experience  and  observation  of  those  who  have 
investigated  the  matter  here  at  home.  It  will,  we  think, 
be  pretty  generally  admitted  that  the  average  inhabi- 
tant of  Europe  does  not  give  evidence  of  that  high  in- 
tellectual development  that  characterizes  the  average 
American.  This  lack  of  mental  development  is  respon-  WHY  THE 
sible  for  the  fact  that  in  factories  in  Europe  which  are  EUROPEAN 
equipped  with  American-made  machines  operated  by  LAGS  IN 
men  working  for  a  much  smaller  wage  than  is  paid  in  PRODUCTION 
this  country,  the  cost  of  production  is  much  higher 
there  than  here.  These  men,  though  steady  and  consci- 
entious in  applying  themselves  to  their  tasks,  do  not 
seem  to  have  the  combination  of  head-heart-and-hands 
so  essential  to  the  speeding-up  methods  in  vogue  here. 
J.  B.  B.  Stryker,  who  had  traveled  somewhat  ex- 
tensively through  Europe  prior  to  the  war  and  who 
visited  numerous  factories,  in  writing  on  the  subject 
says :  "Although  American-made  or  modeled  machin- 
ery is  so  largely  employed  by  them,  the  production  of 
the  average  plant,  comparable  with  ours,  as  to  size, 
equipment  and  number  of  men  employed  falls  consider- 
ably short  of  the  production  over  here."  The  same  may 
be  said  of  the  factory  in  this  country  in  which  the 
average  "foreign  born"  is  placed  in  charge  of  machines 
so  highly  developed  that  all  they  seem  to  require  is 
brain-power,  but  which  deficiency  the  operator  is 
unable  to  supply. 


CHAPTER  XXIII. 

FRICTION   BETWEEN  GLUE  AND  FINISHING 
DEPARTMENTS 

FROM  time  as  far  back  as  the  oldest  glue  room 
man's  memory  goes  there  has  been  more  or  less 
friction  between  the  glue  room  and  the  finishing 
department ;  and  we  do  not  think  a  book  dealing  with 
the  problems  of  the  glue  room  would  be  quite  complete 
were  it  not  to  make  some  effort  to  set  these  depart- 
ments right  in  the  eyes  of  each  other.  It  is  not  our  in-  SHIFTING  THE 
tention  to  take  sides  between  these  departments  RESPONSIBILITY 
further  than  is  merely  incidental  to  the  purpose  of 
bringing  order  out  of  chaos.  The  great  difficulty  be- 
tween these  departments  has  been  and  now  is  that 
when  defects  develop  in  the  work,  each  department  is 
more  interested  in  trying  to  shift  the  responsibility 
from  their  own  to  other  shoulders  than  in  trying  to 
ascertain  the  real  truth  regarding  the  actual  cause  of 
the  trouble.  And  the  fact  that  defects  in  wood  work 
are  not  usually  discovered  until  some  time  after  the 
goods  have  arrived  in  the  finishing  department  and  the 
finishing  process  pretty  well  advanced,  has  tended  to 
intensify  the  difficulty  by  giving  the  glue  room  some 
ground  for  the  assertion  that  the  goods  were  all  right 
when  they  went  into  the  finishing  room,  and  that  some 
material  used  in  the  process  of  finishing  must  be  re- 
sponsible for  the  trouble. 

The  finishing  department,  on  the  other  hand,  when 
defects  develop,  is  equally  positive  that  the  method  of 
finishing  is  not  in  any  way  injurious  to  the  glue  or  in 
any  way  responsible  for  the  defects ;  and  declares  that 
the  defects  were  hidden  in  the  woodwork  before  being 
sent  to  be  finished;  and  that  had  the  glue  men  done 
their  work  right  no  trouble  would  have  ensued.  And 
thus  the  argument  proceeds  ad  infinitum. 

Take,    for    instance,    the    matter    of    blisters    in  VENEER 
veneered  work.    As  a  rule,  these  do  not  show  them-  BLISTERS 
selves  until  the  goods  have  received  at  least  a  coat  of 


146 


MODERN  GLUES  AND  GLUE  TESTING 


WATER  DOES 
NOT  LOOSEN 
THE  VENEER 


TEST  FOR 

LOOSE 

VENEER 


stain — perhaps  of  water  stain.  Or  the  finisher  may 
have  sponged  the  stock  with  water  to  raise  the  grain, 
all  of  which  furnishes  the  glue  man  with  a  lever  with 
which  to  roll  from  his  own  door  to  that  of  the  finishing 
department  the  responsibility  for  the  trouble.  But  let 
us  look  at  the  matter  calmly  for  a  moment.  Let  us  take 
a  piece  of  veneered  work  about  the  soundness  of  which 
there  can  be  no  doubt,  and  let  us  try  and  remove  the 
face  veneer  by  soaking  it  with  water,  using  a  brush  or 
sponge  to  apply  the  water.  We  put  on  one  coat,  two 
coats,  three  coats,  six  coats,  and  still  the  veneer  sticks 
tight.  Now  if  half  a  dozen  applications  of  water  will 
not  loosen  veneer  when  we  want  to  remove  it,  is  it 
reasonable  to  say  that  one  coat  of  water  stain  or  a  light 
sponging  with  water  caused  the  blisters  in  the  finish- 
ing room  ?  Let  us  be  honest  with  ourselves,  even  if  we 
don't  want  to  be  with  the  other  fellow.  We  will  be 
much  wiser  in  the  end  if  we  are. 

If  veneer  is  well  and  truly  laid,  neither  sponging 
nor  one  or  two  coats  of  water  stain  will  loosen  it.  And 
if  it  be  not  well  laid,  or  if  there  be  any  doubt  about  it, 
the  best  thing  that  one  can  do  is  to  go  over  it  with  a 
sponge  and  water  and  by  this  test  ascertain  the  facts. 
A  usual  test  for  blisters  is  to  lightly  tap  the  veneer 
with  the  finger,  and  if  the  response  is  a  sharp  "click" 
we  know  the  veneer  is  loose.  But  this  test  is  not  always 
reliable,  because  the  veneer  may  not  be  cemented  to  the 
core  and  yet  be  lying  sufficiently  close  to  prevent  the 
telltale  click  when  tapped  with  the  finger ;  and  yet  the 
very  moment  it  is  touched  with  water  it  will  raise  in  a 
blister.  Now  why  is  this  so  ?  Let  us  explain : 

The  normal  state  for  the  veneer  would  be  lying  close 
to  the  core ;  it  was  that  way  when  it  left  the  press,  and 
there  has  been  nothing  done  since  to  change  this  condi- 
tion. But  when  we  touch  the  veneer  with  water  we 
change  the  normal  condition  by  causing  the  fibers  to 
swell  and  the  veneer  to  tighten  and  become  too  large 
for  the  place  it  is  in,  and  it  raises  up  to  relieve  the 
strain.  But  it  can  raise  only  if  it  is  already  loose  from 
the  core,  because  if  it  is  firmly  cemented  to  the  core  the 
strain  thus  imposed  could  not  possibly  be  sufficient  to 


FRICTION   BETWEEN   DEPARTMENTS  147 

break  the  glue  joint.  The  same  thing  may  be  illus- 
trated in  another  way:  take  a  sheet  of  paper,  spread 
it  out  on  the  table,  and  draw  a  wet  sponge  part  way 
across  the  center,  and  see  how  quickly  it  wrinkles  up. 
The  moist  piece  at  once  becomes  too  large  for  the  place 
it  occupies  and  expands  in  several  directions.  But  the 
paper  would  not  have  wrinkled  had  it  been  firmly 
cemented  to  a  heavy  body,  which  fact  can  easily  be 
demonstrated  by  the  simple  test  of  trying  to  remove 
wall  paper  by  the  same  process. 

We  recall  the  case  of  a  concern  which  had  more 
than  its  share  of  trouble  with  loose  veneer  and  open 
joints,  without  being  able  to  ascertain  the  cause  TROUBLE  IN 
for  some  time.  The  glue  room  men  and  the  ONE  FACTORY 
cabinet  room  foreman,  under  whose  supervision  the 
glue  room  work  was  done,  all  contended  that  the  cause 
of  the  trouble  lay  hidden  in  the  dark  recess  of  a  large 
oil-stain  vat  into  which  the  stock  was  dipped  on  reach- 
ing the  finishing  room.  Things  were  finally  brought  to 
a  head  by  the  finisher  being  ordered  to  discontinue  the 
use  of  the  vat;  but  he  demanded  some  proof  that  the 
vat  was  the  cause  of  the  trouble.  No  proof  being  forth- 
coming, the  finisher  proposed  to  prove  that  the  vat  was 
not  guilty  as  charged,  and  offered  to  submit  it  to  any 
test  that  might  be  suggested.  To  this  end  a  cake  of  glue 
and  two  or  three  panels  which  gave  evidence  of  being 
sound  were  put  in  the  vat  and  left  there  for  twenty- 
four  hours.  Then,  at  the  end  of  that  time,  the  glue  and 
panels  were  removed,  without  showing  any  evidence  of 
ill  effects  from  their  long  immersion,  the  management 
decided  that  they  must  look  elsewhere  for  the  hidden 
mystery,  and  turned  their  attention  to  the  glue  room. 
When  this  was  done  they  were  not  long  in  finding  what 
they  were  after,  in  the  shape  of  over-cooked  glue  and 
over-heated  cauls.  Having  made  this  discovery,  their 
troubles  from  this  source  were  at  an  end. 

Men  are  not  unlike  mere  material  matter,  in  that 
they  are  prone  to  follow  the  course  of  least  resistance, 
and  in  the  case  under  consideration,  when  defects  are 
found  in  glued-up  work  it  is  much  easier  to  look  for  the 
cause  in  the  immediate  vicinity  of  the  place  where  the 


148 


MODERN  GLUES  AND  GLUE  TESTING 


PLAY  THE 

GAME 

SQUARE 


defects  are  first  discovered  and  find  some  operation, 
the  nature  of  which  we  do  not  understand,  on  which  to 
lay  the  blame,  than  to  make  a  diligent  search  where  we 
are  likely  to  find  out  what  we  are  after.  To  be  quite 
frank  about  it,  it  too  frequently  happens  that  neither 
the  glue  man  nor  the  finisher  is  quite  positive  that  the 
cause  of  the  trouble  is  not  in  his  own  department,  and 
for  this  reason  is  not  very  anxious  to  find  what  he 
is  hunting  for. 

It  is  a  mistake  for  a  man  to  remain  in  ignorance  of 
even  small  matters  merely  because  he  lacks  the  moral 
courage  to  face  the  truth.  There  is  no  man  so  perfect 
that  he  never  makes  mistaks.  Some  one  has  said  that 
"the  man  who  never  made  a  mistake  never  made  any- 
thing that  was  worth  while."  And  it  is  not  the  man 
who  runs  away  from  his  mistakes  or  tries  to  hide  them 
that  succeeds  the  best  in  life.  On  the  contrary,  the  man 
who  succeeds  is  he  who  acknowledges  his  mistakes, 
grapples  with  them  and  overthrows  them  and  uses 
them  as  stepping  stones  to  great  achievements. 

Let  the  finisher  and  the  glue  room  man  determine 
in  his  own  heart  that  he  will  be  honest  with  himself 
and  honest  with  the  other  fellow.  Let  these  two  men 
come  together  with  that  thought  uppermost  in  their 
minds  when  defects  appear  in  glued-up  stock ;  let  them 
together  search  for  the  cause  with  a  determination  to 
find  it,  no  matter  where  it  is  to  be  found,  and  each  will 
find  that  he  has  dropped  many  a  headache,  and  many  a 
heartache  as  well. 


CHAPTER  XXIV. 


VENEERING   SCROLL   WORK. 

ONE  of  the  most  difficult  things  which  the  man 
who  lays  veneer  finds   himself  up   against  at 
times  is  the  problem  of  getting  a  good,  tight  glue 
joint  on  the  scroll  and  other  irregular  work.  To  over- 
come this  difficulty,  various  schemes  have  been  tried  in 
various  places,  with  equally  varying  results.    The  most 
common  practice  is  that  of  applying  extra  pressure  in 
the  hope  that  in  some  way  the  low  spot  where  the 
veneer  is  liable  to  be  loose  will  be  reached   and  suffici- 
ent pressure  applied  to  produce  the  desired  result. 

There  is  one  thing  which  it  would  be  well  for  all  of 
us  to  remember,  and  that  is  that  everything  has  a 
cause,  and  that  a  repetition  of  the  difficulty  before  us 
may  be  avoided  by  removing  the  cause.  When  we  re- 
move the  cause,  the  effect  must  cease.  The  whole  thing  FIND  THE 
may  be  summed  up  in  the  maxim  that  "An  ounce  of  CAUSE 
prevention  is  better  than  a  pound  of  cure."  In  the 
case  before  us,  instead  of  applying  a  sufficient  amount 
of  extra  pressure  to  crush  the  article  out  of  shape,  as 
I  have  often  known  to  be  done,  it  would  be  better  to 
start  at  the  point  of  the  trouble  and  trace  back  until 
we  find  the  cause,  or  the  reason  why  the  pressure  is 
not  uniform  all  over.  Having  found  it,  let  us  remove 
it,  no  matter  what  it  may  be. 

Not  infrequently  the  cause  of  the  difficulty  is  in  the 
design  of  the  article  to  be  veneered.    It  all  too  fre- 
quently happens  that  the  designer  is  not  a  practical 
mechanic,  in  consequence  of  which  the  veneer  man  is 
often  asked  to  do  the  impossible.   Many  times  a  slight 
change  which  would  not  materially  affect  the  appear-  DESIGNS 
ance  of  the  article,  nor  alter  the  designer's  conception,  MUSf  BE 
would  eliminate  mechanical  difficulties  and  greatly  les-  PRACTICAL 
sen  the  manufacturing  cost.    Many  designers  submit 
their  drawings  to  a  practical  man  and  make  the  sug- 
gested alterations.   But  there  are  a  few  who  know  so 
little  about  the  things  of  which  they  are  supposed  to 


150 


MODERN  GLUES   AND  GLUE  TESTING 


DIFFICULTIES 
MUST  BE 
ELIMINATED 


A  LESSON  FOR 
BEGINNERS 


know  considerable  that  they  feel  they  must  guard  that 
little  with  jealous  care — hence  they  resent  any  sugges- 
tions regarding  the  offspring  of  their  brain.  When  I 
find  one  of  these  men  I  cannot  help  making  him  an  ob- 
ject of  mingled  pity  and  contempt.  Pity  because  he  is 
small,  and  will  never  be  any  bigger.  The  designer  who 
is  worthy  the  name  has  nothing  to  fear.  He  is  a  big 
man  in  the  profession.  He  has  had  his  eyes  open  to  see 
and  his  ears  open  to  hear  anything  that  might  be  sug- 
gested to  him.  But  the  small  man — he  is  small  because 
he  refused  to  open  his  mind  to  imbibe  that  which  would 
have  made  him  big.  Under  the  most  favorable  condi- 
tions it  is  not  an  easy  matter  to  get  a  first-class,  de- 
pendable glue  joint  on  scroll  work;  hence  the  impor- 
tance of  eliminating  everything  that  would  make  it 
more  difficult. 

But  even  where  every  care  has  been  taken  by  the 
designer  to  remove  all  unnecessary  difficulties,  it  is  not 
always  possible  for  the  veneer  layer  to  produce  the  de- 
sired result,  although  through  no  fault  of  his  own,  and 
in  consequence  of  something  over  which  he  has  no  con- 
trol. It  is  the  common  practice,  and  rightly  so,  to  use 
as  a  caul  the  piece  bandsawed  from  the  scroll.  Now,  in 
order  to  make  ourselves  quite  clear,  let  us  discuss  the 
matter  before  us  as  though  we  were  presenting  it  to  a 
class  of  boys  in  school.  Let  us  take  the  scroll  to  be 
veneered  and  lay  it  on  its  side  on  the  bench ;  then  take 
the  piece  which  was  cut  away,  and  which  we  are  to  use 
as  a  caul  ,and  lay  it  beside  the  scroll,  being  careful  to 
have  the  two  pieces  separated  by  the  thickness  of  the 
saw  which  was  used  to  cut  the  two  apart.  Having  done 
this,  we  will  look  along  the  various  curves  and  lines 
and  we  will  observe  that  at  all  points  the  distance  be- 
tween the  two  pieces  is  exactly  the  same.  If  we  move 
them  a  little  closer  together  we  will  .observe  that  at 
certain  points  they  are  nearer  each  other  than  at  other 
points.  The  same  thing  will  be  seen  if  we  move  them 
farther  apart  instead  of  closer  together.  If  we  move 
the  two  pieces  together  until  they  meet  we  will  see  that 
they  touch  at  certain  points  only.  Now,  in  what  we 
have  just  pointed  out  is  to  be  found  the  reason  why  it 


VENEERING   SCROLL   WORK 


151 


is  so  difficult  to  get  a  good,  tight  glue  joint  between  the 
veneer  and  the  surface  of  the  scroll  on  which  it  is  laid ; 
and  in  the  same  thing  is  to  be  found  a  solution  of  the 
problem  which  the  subject  presents.  To  illustrate : 

Suppose  we  bandsaw  a  scroll,  using  a  saw  set  to 
make  a  cut  1/20-in.  in  width.  Having  done  this,  we 
place  the  scroll  and  the  caul  on  the  bench  separated  by 
exactly  1/20-in.  at  any  one  point  and  we  will  see  that 
they  are  an  equal  distance  apart  at  all  points.  Now 
take  a  piece  of  veneer  1/20-in.  in  thickness  and  slip  it 
in  between  the  caul  and  the  scroll,  and  you  will  find 
that  the  fit  is  perfect  at  all  points. 

Now,  suppose  we  remove  the  1/20-in.  veneer  and 
substitute  a  piece  1/30-in.  in  thickness,  and  press  the 
caul  and  scroll  together  to  fill  in  the  space  resulting 
from  the  difference  in  the  thickness  of  the  two  veneers 
and  we  will  find  that  at  certain  points  the  veneer  is 
tight,  while  at  other  points  it  is  quite  slack. 

Now,  let  us  remove  the  1/30-in.  piece  of  veneer  and 
fill  the  space  with  a  piece  1/16-in.  thick  and  we  will  find 
the  conditions  the  very  reverse  of  what  they  were 
before;  the  points  which  were  tight  with  the  1/30-in. 
veneer  are  now  slack ;  and  where  it  was  formerly  slack 
it  is  now  tight. 

All  this  goes  to  show  that  the  problem  of  a  tight 
glue  joint  on  scroll  work  is  in  the  use  of  a  veneer  ex- 
actly the  same  thickness  as  the  kerf  removed  by  the 
saw.  Of  course,  there  are  other  things  of  importance 
to  be  attended  to.  Good  judgment  must  be  exercised  in 
applying  the  pressure.  Where  the  pressure  must  be 
applied  from  two  directions  it  should  be  applied  to  the 
smaller  surface  first,  otherwise  it  may  be  found  diffi- 
cult, if  not  in  some  instances  impossible,  to  overcome 
the  resistance  offered  by  the  greater  pressure  on  the 
larger  surface  to  insure  a  tight  joint  at  these  smaller 
points. 


VENEER  MUST 
BE  THICKNESS 
OF  SAW  KERF 


CHAPTER  XXV. 

LAYING  FINE  FACE  VENEERS. 

THE  first  requisite  to  the  successful  laying  of  face 
veneer  for  fine  cabinet  work  is  the  quality  of  the 
veneer  itself.    We  may  have  a  good  core  well 
crossbanded ;  and  we  may  employ  the  most  skilled  help 
to  do  the  work  with  the  best  of  glue ;  but  if  the  veneer 
is  of  a  poor  quality  our  work  will  count  for  naught.  It 
is  not  enough  that  veneer  be  well  figured  to  be  classed 
as  good  stock ;  it  must  be  well  cut,  and  well  cared  for, 
and   well   dried — otherwise   we   are   merely   building 
trouble  for  the  future  into  our  work. 

A  great  deal  of  our  best  figured  veneer  has  the 
fiber  so  badly  ruptured  as  to  make  it  extremely  diffi- 
cult, if  not  quite  impossible,  to  lay  it  with  any  degree  of 
assurance  that  trouble  will  not  develop;  and  for  this 
reason  one  should  exercise  the  utmost  care  in  selecting 
the  stock  for  fine  face  work.  The  more  beautiful  the 
figure  of  the  wood,  the  more  difficult  it  is  to  cut  into  GOOD 
veneer  without  doing  damage  to  the  fibers.  The  figure  K 
is  the  result  of  the  entwining  and  interlacing  of  the 
wood  fibers  in  such  a  way  that  when  cut  into  veneer 
many  of  the  fibers  are  cut  into  lengths  no  longer  than 
the  thickness  of  the  veneer,  which  may  be  as  fine  as 
1/30-in.,  and  sometimes  even  less.  These  short  fibers, 
which  run  straight,  or  almost  so  from  one  side  of  the 
veneer  to  the  other,  make  what  is  called  "end  wood ;" 
and  unless  the  veneer  is  handled  very  carefully  it  is 
very  liable  to  check  at  these  places.  It  also  makes  it 
very  difficult  to  dry  without  checking,  as  the  difference 
in  the  grain  is  such  that  some  parts  dry  out  faster  than 
others;  and  this  uneven  drying  means  uneven  shrink- 
ing, and  this  sets  up  strains  in  the  wood  which  certain 
parts  are  unable  to  withstand;  and  they  break.  For 
this  reason,  veneer,  when  once  dry,  should  be  kept  dry, 
in  order  to  reduce  to  a  minimum  the  possibility  of 
checking. 

But  too  much  care  cannot  be  exercised  to  insure  the 


154 


MODERN  GLUES  AND  GLUE   TESTING 


A  REDRYER  IS 
NECESSARY 


FLATTEN   OUT 

BUCKLED 

VENEER 


veneer  being  dry  before  laying.  It  would  be  safe  to  say 
that  nine-tenths  of  the  trouble  with  veneered  work  re- 
sults from  the  veneer  not  being  dry  at  the  time  of  lay- 
ing ;  or,  more  properly  speaking,  at  the  time  the  press- 
ure is  applied.  We  may  have  the  veneer  thoroughly  dry 
at  the  time  of  laying  on  the  core,  and  by  leaving  it  loose 
so  that  it  absorbs  moisture  from  the  glue  and  swells 
before  the  pressure  is  applied  we  may  defeat  all  our 
efforts  in  drying. 

Where  one  has  considerable  veneering  to  do  it  will 
pay  to  put  in  a  redryer.  It  is  not  our  intention  to  advo- 
cate the  claims  of  any  one  make,  as  all  have  merits 
worth  considering;  and  the  buyer  must  be  guided  by 
the  work  in  hand  and  select  the  machine  best  adapted 
to  meet  his  own  peculiar  requirements.  But  if  one  is 
starting  in  a  small  way,  or,  for  instance,  in  a  manual 
training  school,  it  would  not  be  the  part  of  wisdom  to 
go  to  the  expense  of  installing  an  expensive  redryer. 
Under  such  circumstances  one  must  adopt  other  means 
to  accomplish  the  desired  result.  Take  boards  of  some 
soft,  absorbing  wood,  such  as  basswood,  and  cut  them 
in  size  a  little  larger  than  the  veneer  to  be  redryed. 
Heat  these  boards  as  hot  as  possible  in  the  hot-box  and 
lay  the  sheets  of  veneer  between  the  boards,  keeping 
each  sheet  separate,  and  put  under  pressure,  applying 
a  heavy  pressure  for  a  few  moments  at  the  start  to 
allow  the  veneer  to  heat  quickly ;  then  loosen  the  press- 
ure to  allow  the  veneer  to  shrink,  as  the  boards  absorb 
the  moisture,  without  the  danger  of  checking. 

Much  of  the  finest  face  veneer,  such  as  crotch  and 
burl  walnut,  is  badly  buckled  when  dry,  and  cannot  be 
laid  in  this  condition  without  breaking  when  the  press- 
ure is  applied.  Stock  of  this  kind  may  be  moistened 
with  water  sufficiently  to  allow  it  to  be  flattened  out 
with  safety,  then  redried  in  the  manner  described 
above. 

For  the  benefit  of  any  who  may  not  know  what  the 
hot-box  is  spoken  of  above  it  might  be  well  to  describe 
the  form  of  construction.  There  are  many  different 
ways  of  making  hot-boxes ;  some  being  made  of  boards, 
but  the  principle  is  the  same  in  each  case  and  we  will 


LAYING   FINE   FACE   VENEERS  155 

describe  the  box  which  we  think  to  be  the  best.  It  is  a 
metal  box  made  from  sheet  iron.  If  a  large  box  is  re- 
quired it  is  made  in  sections  fastened  together  with 
angle-irons.  The  sheet-iron  is  made  into  panels,  two  SHEET 
sheets  to  a  panel  with  sheet  asbestos  in  the  center.  Into  IRON 
this  box  steam  pipe  coils  are  placed  in  such  a  way  that  HOT  BOX 
they  may  be  used  as  shelves ;  the  number  of  shelves  and 
the  distance  apart  depending  on  the  size  of  the  box 
and  the  work  to  be  done.  This  box  is  different  from  a 
drying  room;  the  idea  here  being  to  get  a  maximum 
heat  in  a  minimum  time.  For  heating,  either  exhaust 
or  live  steam  may  be  used.  If  a  trap  is  placed  at  the 
outlet  of  the  coils  it  will  cost  very  little  to  heat  with 
live  steam.  The  stock  to  be  heated  is  placed  on  the 
coils  of  pipe.  There  should  be  a  vent  at  the  top  of  the 
box  to  allow  any  moisture  that  may  be  present  to 
escape ;  as  the  boards  to  be  heated  must  be  absolutely 
devoid  of  moisture  to  do  the  best  work. 

With  the  stock  thoroughly  dry  it  is  ready  to  be 
jointed  and  taped  if  it  is  narrow  stock.  Whether  ore 
has  a  taping  machine  in  his  factory  should  depend  on 
the  amount  of  work  he  has  to  do ;  but  one  man  with  a 
taping  machine  can  tape  as  much  stock  as  half  a  dozen 
men  can  by  hand;  and  as  the  machines  are  compara- 
tively inexpensive,  it  would  be  well  to  give  the  matter 
very  serious  consideration  before  deciding  that  you  can 
afford  to  do  without  one. 

The  usual  method  of  taping  veneer  is  to  tack  one 
piece  to  a  board,  using  very  fine  brads  for  the  purpose,  TAPING 
so  as  not  to  make  too  large  a  hole,  then  fitting  the  edge  VENEER 
of  the  second  piece  close  to  the  edge  of  the  first  piece, 
being  careful  to  match  the  grain  and  figure,  and  tack- 
ing it  down  in  like  manner.  But  this  method  has  disad- 
vantages as  it  takes  time  to  tack  the  veneer  to  the 
board  as  well  as  time  to  remove  it  after  the  taping  has 
been  done.  The  tack  holes  must  also  be  considered,  for, 
no  matter  how  careful  one  may  be,  and  no  matter  how 
small  a  brad  he  may  use,  in  some  veneer  the  mark  will 
show. 

A  better  way  to  tape  by  hand,  but  one  which  re- 


156 


MODERN  GLUES  AND  GLUE  TESTING 


First  operation:     Moisten  tape  and  run  it  along  edge  of  veneer, 
allowing  one-half  to  project  over  for  the  next  piece 


Veneer  reversed  with  gummed  side  of  tape  up  ready  to 
receive  its  mate 


The  two  pieces  joined  ready  for  laying 
FIG.  22 


LAYING   FINE   FACE   VENEERS 157 

quires  some  skill,  especially  with  long  joints,  is  to  place 
the  sheet  of  veneer  on  the  taping  bench  with  the  side  to 
be  taped  upward  (Figure  22.)  Moisten  the  tape  and 
run  it  along  the  edge  of  the  veneer;  one-half  on  the 
veneer  and  the  other  half  projecting  over.  Then  turn 
the  veneer  over.  This  brings  the  gummed  side  of  the 
tape  upward  ready  to  receive  the  second  piece  of 
veneer.  Speed  and  skill  are  necessary  to  get  both 
j)ieces  in  position  while  the  tape  is  sufficiently  moist 
to  take  a  good  hold ;  but  with  a  little  practice  one  can 
become  most  proficient. 

Never  spread  the  glue  on  the  veneer,  as  to  do  so  will  SPREAD  THE 
destroy  all  the  good  effects  of  redrying.      After  the  GLUE  ON 
glue  has  been  spread  on  the  core  it  should  be  allowed  to  THE  CORE 
set  for  a  few  minutes  to  become  slightly  "tacky."  This 
will  allow  some  of  the  moisture  to  penetrate  the  core 
where  it  will  be  comparatively  harmless;  otherwise 
much  of  it  will  enter  the  veneer  before  it  can  be  gotten 
under  pressure.  And  let  us  say  to  get  the  stock  under 
pressure  at  the  earliest  possible  moment  after  the 
veneer  touches  the  glue  in  order  to  prevent  the  veneer 
swelling  through  the  absorption  of  moisture  from  the 
glue. 

And  in  this  connection  let  us  not  confuse  cause  and 
effect.  In  removing  moisture  from  veneer  by  the  pro  • 
cess  known  as  redrying  we  have  two  objects  in  view. 
It  is  very  seldom  that  veneer  which  has  once  been  dried 
contains  a  sufficient  amount  of  moisture  to  prove  a 
detriment  to  the  glue;  hence  the  removal  of  the  mois- 
ture is  of  secondary  consideration.  Moisture  in  veneer 
is  a  cause  and  not  an  effect.  It  is  the  cause  of  expan- 
sion in  the  veneer ;  and  it  is  to  decrease  this  expansion 
that  we  remove  the  moisture.  If  the  veneer  is  laid  in  to 
this  expanded  condition  and  becomes  firmly  cemented 
to  the  core  it  cannot  shrink  back  to  its  normal  width 
during  the  process  of  drying  the  built-up  stock — that 
is,  it  cannot  draw  in  from  the  edges.  The  fibers  them- 
selves will  shrink,  and  will  separate  one  from  the 
other,  making  very  fine  checks  in  some  instances;  and 
in  others  larger  ones.  It  is  to  prevent  this  that  we  re- 
move the  moisture  before  laying  the  veneer  when  it 


158 


MODERN  GLUES  AND  GLUE   TESTING 


EXPANSION 

AND 

CONTRACTION 


OPEN 
JOINTS 


can  shrink  to  a  minimum  width  without  injury  to  the 
fibers. 

To  prevent  the  veneer  expanding  through  absorb- 
ing moisture  from  the  glue  we  advise  getting  the  stock 
under  pressure  as  soon  as  possible  after  glue  and 
veneer  come  together.  There  are  many  who  have  the 
idea  that  so  long  as  the  veneer  was  made  thoroughly 
dry  before  being  laid  all  danger  along  this  line  has 
passed;  but  a  more  fallacious  idea  could  scarcely  be 
entertained.  It  is  at  this  point  that  the  real  danger 
exists.  It  is  seldom  that  a  veneer  which  has  once  been 
dried  will  contain  as  large  a  percentage  of  moisture 
before  being  laid  as  will  be  found  in  a  redried  veneer 
two  minutes  after  it  has  come  in  contact  with  the  glue. 
One  should  not  lose  sight  of  the  fact:  It  makes  no 
difference  how,  when  or  where  the  veneer  gets  the 
moisture  that  expands  it — whether  the  dews  of  heaven 
descend  upon  it;  whether  it  gets  it  from  the  atmos- 
phere during  a  period  of  high  humidity  or  gets  it  from 
the  glue  just  prior  to  going  under  pressure,  the  effect 
is  the  same — expansion.  And  it  makes  no  difference 
how,  when  or  where  this  expansion  was  brought  about, 
the  effect  is  the  same — contraction ;  and  the  inevitable 
result  of  the  shrinking  veneer  after  it  is  laid  is :  checks. 

Not  a  few  people  have  trouble  with  butt  joints 
opening  after  the  veneer  is  laid.  These  openings  are 
not  always  uniform ;  and  they  do  not  always  extend  the 
full  length  of  the  joint.  This  has  frequently  given  rise 
to  the  suggestion  that  the  man  who  jointed  and  taped 
the  stock  was  careless  about  his  work;  and  has  fre- 
quently resulted  in  much  confusion  and  no  little  ill  feel- 
ing. But  no  matter  how  well  stock  may  be  jointed  and 
raped  it  will  open  in  certain  places  if  allowed  to  absorb 
moisture  from  the  glue  before  it  receives  the  pressure. 

Wood  does  not  expand  uniformly  at  all  points.  In 
the  case  of  crotch  veneer  the  difference  in  fiber  and 
texture  of  the  different  figures  allows  great  scope  for 
this  uneven  swelling;  and  when  those  places  along  the 
edge  of  the  joint  which  expand  more  rapidly  than 
others,  do  so,  and  press  against  each  other  they  sepa- 


LAYING   FINE   FACE   VENEERS 159 

rate  the  slower  swelling  parts — hence  the  uneven,  open 
joint. 

The  remedy  for  this  is  the  same  as  for  checks,  i.  e., 
get  the  pressure  on  before  the  veneer  can  swell,  for 
under  heavy  pressure  it  cannot  move.  THE  LESSER 

In  laying  crotch  veneer  on  ogee  drawer  fronts  and  OF  TWO 
other  shaped  work  some  have  resorted  to  moistening  EVILS 
the  veneer  with  water  to  prevent  breaking.  This  is  all 
right  as  far  as  it  goes ;  but  it  does  not  go  far  enough. 
Those  who  follow  this  practice  admit  they  have  plenty 
of  trouble  with  the  veneer  checking;  but  they  claim 
the  checks  are  not  as  bad  as  would  result  from  laying 
the  veneer  when  dry ;  and  of  two  evils  they  are  choos- 
ing the  least. 

But  there  is  no  necessity  for  making  a  choice  be- 
tween these  two  evils ;  for  both  may  easily  be  avoided. 
Make  some  forms — duplicates  of  the  forms  to  be  ve- 
neered ;  using  basswood,  or  some  other  absorbing  wood 
for  the  purpose;  and  heat  them  in  the  hot-box. 
Moisten  the  veneer  with  water  to  render  it  pliable ;  and 
when  sufficiently  so  bend  it  to  shape  in  the  duplicate 
forms  under  pressure  the  same  as  when  laying  the  ve- 
neer permanently.  The  usual  amount  of  moisture  in 
veneer  thus  treated  will  make  it  difficult  for  one  form 
to  insure  its  complete  elimination.  For  this  reason  it 
would  be  well  to  either  re-heat  the  forms  and  make  a 
second  application,  or  place  the  veneer  in  the  drying 
room  for  a  short  time.  It  will  retain  its  form,  so  that 
no  trouble  need  be  anticipated  from  that  direction. 

Where  animal  glue  is  used  for  veneer  it  is  necessary 
to  use  warm  (not  hot)  cauls,  which  help  to  keep  the  ugE 
glue  in  a  liquid  state  for  a  longer  period  of  time  than  WARM 
would  otherwise  be  the  case,  enabling  it  to  more  firmly  CAULS 
unite  with  the  wood.   Let  us  lay  emphasis  on  the  im- 
portance of  the  cauls  being  at  the  right  temperature. 
The  heat  in  the  caul  helps  to  diffuse  the  moisture  in  the 
glue ;  driving  it  into  the  core ;  and  the  hotter  the  caul 
the  more  rapidly  it  drives  it  away.  This  is  as  it  should 
be,  for  in  the  core  the  moisture  can  do  no  harm.  But  if 
the  caul  is  not  hot  this  rapid  diffusion  of  the  moisture 
creates  a  source  of  danger,  as  it  leaves  the  glue  in  a 


160 MODERN  GLUES  AND  GLUE  TESTING 

dry  state  devoid  of  the  protection  of  the  moisture,  in 
which  condition  it  is  very  easily  injured  by  heat.  This 
CAULS  SHOULD     can  be  better  understood  when  we  remember  that  the 
NOT  BE  heat  required  to  prepare  the  glue  for  use  would  render 

it  absolutely  useless  were  it  not  for  the  protection 
furnished  by  the  water  which  it  contains.  Cauls 
should  never  be  made  so  hot  that  they  cannot  be  read- 
ily handled  with  the  bare  hands,  in  which  condition 
they  can  do  no  harm. 


CHAPTER  XXVI. 

SPREADING  THE  GLUE 

ONE  cannot  do  good  work  with  inferior  glue,  but 
he  can  do  very  poor  work  with  the  best  glue  if 
he  does  not  use  it  right.  The  glue-mixer  may 
have  his  solution  in  the  best  possible  condition,  but  all 
his  care  will  be  far  nought  unless  those  who  use  it 
afterward  understand  what  is  required  of  them.  "The 
chain  is  no  stronger  than  its  weakest  link"  is  a  maxim 
no  more  true  anywhere  than  here.  All  through  the 
process  of  building  glued-up  stock  every  detail  requires 
intelligent  and  careful  attention,  otherwise  there  will 
be  a  weak  link  in  the  chain  of  operations  because  of 
some  neglected  detail  and  the  work  will  fall  down  at 
that  particular  point. 

The  spread  of  glue  must  be  uniform  and  of  the  cor- 
rect weight.   For  this  reason  glue-spreading  machines 
are  preferable  to  the  old-time  brush  and  glue  pot,  as 
the  spread  is  evenly  placed  all  over  each  piece  and  each  GLUE  SPREAD 
piece  is  spread  alike.  But  the  operator  of  the  mechani-  MUST  BE 
cal    glue-spreader    must    understand   the    weight    of  EVEN 
spread  required  for  the  work  in  hand,  otherwise  the 
spread  may  be  too  heavy  or  too  light  and  defective 
work  will  result. 

Much  poor  work  results  from  a  too  heavy  applica- 
tion of  a  heavy  glue  solution.  It  is  obvious  that  an  in- 
sufficient quantity  of  glue  to  the  joint  will  result  in 
defects  sooner  or  later ;  but  not  every  one  can  see  that 
an  over-application  of  glue  is  equally  bad.  If  one  puts 
on  an  excessive  amount  of  glue  of  a  heavy  consistency 
and  allows  it  to  stand  until  it  becomes  tacky  there  is 
danger  of  the  surplus  not  squeezing  out,  and  thus  leav- 
ing an  excessive  amount  in  the  joint.  Where  this 
occurs,  the  glue,  in  shrinking  during  the  process  of 
drying,  is  much  more  liable  to  break  away  from  the 
veneer,  allowing  the  latter  to  raise  in  places  in  the 
form  of  blisters. 

The  modern  mechanical  glue-spreader  has  one  seri- 


162 


MODERN  GLUES  AND  GLUE  TESTING 


INTELLIGENCE 
IS  NEEDED 


LOOK   FOR 
THE  CAUSE  OF 
FOAM 


ous  defect — it  has  no  brains;  but  I  am  sometimes 
inclined  to  think  that  it  has  about  as  much  of  tnat  com- 
modity as  many  men  who  are  allowed  to  spread  glue 
with  a  brush  in  some  shops.  Some  employers  appear 
to  have  the  idea  that  the  mechanical  glue-spreader  has 
brains  of  its  own,  and  that  a  further  supply  is  unneces- 
sary, and  they  put  a  man  in  charge  of  the  machine  who 
gives  no  evidence  of  being  in  possession  of  that  prime 
necessity. 

From  almost  every  viewpoint  the  mechanical  glue- 
spreader  is  essential  to  the  success  of  the  veneering 
department ;  and  especially  is  it  an  economic  necessity. 
It  will  do  more  and  better  work  than  can  be  done  at 
the  same  cost  when  done  by  hand;  and  it  conserves 
glue,  which  is  no  inconsiderable  item  at  the  present 
time  with  the  prevailing  high  prices.  More  glue  than  is 
necessary  is  not  put  on  the  stock ;  and  the  glue  is  not 
wasted  by  splashing  everything  around.  In  many 
plants  the  saving  of  glue  through  the  prevention  of 
waste  alone  would  soon  pay  for  the  machine. 

In  operating  the  mechanical  glue-spreader  one 
must  give  special  attention  to  the  speed,  for  if  run  too 
fast  it  will  unduly  agitate  the  glue  and  cause  it  to  foam. 
If  the  glue  should  foam,  suspend  operations  at  once 
until  the  cause  of  the  foaming  has  been  ascertained. 
Some  glue  will  foam  much  more  readily  than  others 
for  which  there  may  be  various  causes.  If  the  foaming 
continues  under  a  reduced  speed  the  cause  will  be  in 
the  glue ;  the  thing  then  to  do  is  to  examine  local  con- 
ditions to  ascertain  if  the  cause  of  the  trouble  is  in  the 
shop  or  came  with  the  glue. 

If  the  glue  is  fresh  and  the  dissolver  was  clean  be- 
fore the  glue  was  mixed,  and  the  spreader  was  thor- 
oughly cleaned  before  it  received  the  solution  and  the 
glue  has  not  been  overheated,  then  it  is  pretty  safe  to 
conclude  that  the  cause  is  not  local ;  but  is  inherent  in 
the  glue. 

Some  experiments  have  shown  that  glue  foaming 
may  be  caused  by  the  entire  absence  of  grease  from 
the  glue.  Good  glue  intended  for  brush  work  usually 
contains  no  grease,  this  having  all  been  extracted  dur- 


SPREADING  THE   GLUE 163 

ing  the  process  of  making.  When  such  glue  is  intended 
for  the  spreader,  and  the  manufacturer  knows  the  pur- 
pose for  which  it  is  intended  he  will  usually  add  a  suffi- 
cient quantity  of  cocoanut  oil  to  prevent  foaming.  A 
serious  case  of  foaming  has  been  checked  by  adding  a 
piece  of  beef  tallow  the  size  of  a  marble  to  each  gallon 
of  the  glue  solution.  This  amount,  though  sufficient  to 
prevent  foaming,  would  have  no  appreciable  effect  on 
the  adhesive  quality  of  the  glue. 

There  are  other  causes  of  foaming,  but  all  point  to  GOOD  WORK 
inferiority  in  quality.    Cheap  bone  glues  are  prone  to  REQUIRES 
foam  when  used  in  the  spreader;  and  glue  that  has  GOOD  QLUE 
been  over-limed  will  do  likewise.    Such  glues  should 
not  be  used  where  good  work  is  expected  to  result. 


CHAPTER  XXVII. 

THE  GLUE  SALESMAN. 

SALESMANSHIP  has  been  advanced  to  a  science. 
It  is  no  longer  a  wierd  and  mysterious  magic  by 
which  one  man  influences  another  to  buy  from 
him  an  article  which  he  may  or  may  not  want.    It  is  no 
longer,  as  it  was  in  the  early  ages,  an  exchange  of 
necessary  commodities.   It  is  no  longer  a  happy  hunt- 
ing ground  for  the  shrewd  and  unscrupulous,  but  it  has  THE  SCIENCE 
evolved  from  its  first  stages  of  necessary  exchange,  OF  SALES- 
through  all  the  mazes  of  charlatanry,  bringing  with  it  MANSHIP 
the  best  from  each  stage,  until  it  has  grown  into  a  sci- 
ence and  profession.    Slower  than  the  professions  of 
the  physician  and  chemist  in  its  development,  it  has, 
however,  reached  a  degree  now,  in  which  it  is  building 
Its  own  etiquette  and  coming  to  its  own  recognition. 

In  view  of  this  modern  science  of  salesmanship,  I 
shall  attempt  to  give  my  ideas  of  the  scientific  selling 
of  glues. 

It  is  very  true  that  there  are  certain  lines  of  busi- 
ness in  which  the  salesman  has  no  competition;  this, 
however,  is  the  exception.  There  are  many  lines  in 
which  the  competition  is  more  imaginary  than  real; 
that  is  to  say,  the  quality  of  the  goods  of  the  so-called 
competitor  is  so  much  inferior  to  that  of  the  goods  car- 
ried by  a  first-rate  manufacturer  that  there  is  no  reaJ 
competition.  The  buyer,  however,  who  is  usually 
shrewd,  and,  unfortunately  is  often  unscrupulous,  will, 
if  possible,  lead  the  salesman  to  think  that  competitors 
have  given  better  prices  or  better  terms,  and  that  their 
goods  are  superior.  The  salesman  who  is  not  armed  at 
every  point  to  meet  his  tactics  runs  the  risk  of  being 
imposed  upon. 

We  know  absolutely  that  most  manufacturers,  job-  THE  CUSTOMER 
bers  and  dealers  of  glues  desire  to  please  the  customer  MUST  BE 
and  will  endeavor  in  every  way  to  hold  up  the  grade  PLEASED 
that  is  being  bought.  These  men  know  absolutely  that 
many  buyers  will  try  to  buy  glues  at  low  prices  and 


166 


MODERN  GLUES  AND  GLUE  TESTING 


SALESMEN 
MUST  KNOW 
THE  GAME 


DON'T  KNOCK 

THE  OTHER 

FELLOW'S 

GOODS 


some  buyers  may  "bluff"  the  salesman.  In  most  cases 
it  has  been  due  to  the  salesman's  ignorance  that  the 
sale  was  lost.  Again,  nothing  will  destroy  a  buyer's 
confidence  more  quickly  than  to  find  a  salesman  ignor- 
ant of  the  claims  made  by  his  own  house,  or  of  the  spe- 
cific qualities  of  the  glues  offered  for  sale.  All  sales- 
men need  to  keep  themselves  fresh  and  enthusiastic  in 
regard  to  their  goods,  not  only  by  frequently  visiting 
their  factories,  keeping  in  touch  with  the  qualities  of 
all  boilings,  but  also  by  reading  all  literature  applica- 
ble to  glue  and  glue  testing.  Therefore,  do  not  super- 
ficially peruse  the  pages  of  this  valuable  book.  Read  all 
the  material  contained  herein  time  and  again  and  the 
writer  knows  absolutely  that  if  the  information  is  ap- 
plied, the  salesman's  success  is  assured. 

Get  all  the  information  you  can  from  the  salesmen 
of  competing  factories.  Learn  all  you  can  in  an  open 
fair  way,  but  do  not  resort  to  trickery,  or  to  any  meth- 
ods which  you  would  be  unwilling  to  have  a  competitor 
use  with  your  house.  Do  not  attempt  to  sell  goods  until 
you  know  absolutely  that  you  can  meet  any  argument 
and  that  your  line  of  talk  is  of  such  character  that 
there  will  be  no  doubt  in  the  mind  of  the  buyer  that  you 
are  not  a  novice,  not  a  traveling  man  trying  to  put 
something  over,  but  a  real  glue  salesman  in  all  that  the 
name  implies. 

It  is  to  be  regretted  that  there  actually  are  glue 
salesmen  who  seem  to  delight  in  "knocking  their  com- 
petitors." I  have  met  men  who  deliberately  knocked 
high  grade  glues,  comparing  them  in  quality  with  low 
grade  products.  A  certain  salesman  sold  hundreds  of 
tons  of  grade  1^4  glue  for  joint  purposes  and  claimed 
his  glue  would  compare  wi£h  any  joint  glue  regardless 
of  price.  His  argument  was  that  his  glue  did  rot  take 
as  much  water  as  most  hide  glues,  but  it  is  of  the  high- 
est quality  as  a  joint  product.  Very  fortunately  the 
writer  made  joint  determinations  in  the  presence  of 
the  salesman  and  his  glue  was  used  in  the  test.  This 
man  has  not  called  at  my  office  since  and  he  did  finally 
say:  "It  takes  a  salesman  to  get  by  with  my  line  of 
'stuff,'  but  the  man  selling  high  grade  glues  at  a  reas- 


THE   GLUE   SALESMAN 167 

enable  or  low  price  is  not  a  salesman  but  an  order 
taker." 

So  many  salesmen  seem  to  suppose  that  business  is 
done  largely  on  friendship.  "Friendship  and  business 
don't  mix,"  is  an  old  adage  and  a  true  one.  You  can't 
presume  on  your  intimacy  with  a  man  to  sell  him 
goods;  and  it  is  seldom  you  can  get  his  trade  away 
from  a  successful  salesman,  even  if  you  have  identical 
grades  and  quote  the  same  prices.  There  is  no  doubt 
that  business  friendship  plays  a  very  large  part  in 
business  getting  with  all  salesmen.  You  know  how 
hard  it  often  is  to  break  in  on  the  trade  of  another 
man,  simply  because  he  has  won  the  friendship  of  his  DON'T  PRESUME 
customers.  Keep  this  in  mind,  but  please  remember  TOO  MUCH  ON 
that  if  your  goods  are  right  and  the  price  reasonable,  FRIENDSHIP 
you  have  nothing  to  fear,  especially  so  if  you  merit  the 
confidence  of  your  trade.  I  have  known  of  buyers  pur- 
chasing glues  from  one  factory  for  more  than  thirty 
years.  They  finally  came  to  their  senses  though  and 
now  every  reputable  glue  house  known  to  them  gets  a 
chance  at  their  business. 

To  be  a  successful  glue  salesman  it  is  absolutely  es- 
sential to  become  familiar  with  practically  all  the  dif- 
ferent lines  employing  glues  or  other  adhesives  in  their 
work.  For  instance,  in  selling  glues  to  manufacturers 
of  wall  paper  it  is  necessary  to  offer  only  such  glues  as 
are  free  from  foam.  The  glue  must  also  be  free  from 
mucin  and  soaps  which  will  not  affiliate  with  the  colors 
or  clay.  He  will  not  offer  glues  to  textile  manufactur- 
ers containing  mineral  acids  and  normal  sulphites 
since  any  notable  proportions  of  these  impurities  will 
reproduce  light  patches  on  dyed  wool.  He  is  also  very 
careful  in  offering  glues  free  from  coloring  agents  that 
will  injure  the  shades  of  silks.  He  knows  that  pale 
glues  have  been  bleached  with  sulphuric  acid,  traces, 
and  frequently  more  than  traces  of  which  remain  in 
the  glue,  as  well  as  salts  of  sulphurous  acid.  When  sell- 
ing to  manufacturers  of  paper  boxes,  the  salesman 
appreciates  that  either  animal  .or  the  vegetable  glues 
may  be  used  to  good  advantage.  He  knows  that  where 
gloss  or  the  finish  of  a  good  covering  paper  has  to  be 


168 


MODERN  GLUES  AND  GLUE  TESTING 


MANY  USES 
FOR  GLUE 


THE  SALESMAN 
SHOULD  MAKE 
SIMPLE  TESTS 


preserved,  the  animal  glue  has  preference.  When 
asked  why  he  will  say,  because  the  pastes,  and  some 
gums  have  so  much  water  in  them  that  the  gloss  is  im- 
paired. He  also  knows  that  the  drawbacks  of  animal 
glues  are  higher  prices  and  that  in  this  respect  the 
vegetable  glues  have  the  advantage.  Mr.  Glue  Sales- 
man does  not  lose  sight  of  the  fact  that  various  box 
factories  offer  different  problems  and  every  problem 
deserves  study  and  well  "thought  out"  solutions.  In- 
deed, there  is  hardly  an  article  manufactured  in  the 
making  of  which  glue  does  not  play  a  very  important 
part  in  some  form  or  other. 

The  salesman  should,  if  possible,  be  practical.  Some 
of  the  things  that  the  salesman  can  do  along  this  line 
are  trivial.  Some,  on  the  other  hand,  are  big.  The 
representative  who  can  give  the  men  in  the  glue  room 
valuable  tips,  is  always  welcome  and  the  superinten- 
dent or  foreman  may  ask  the  purchaser  of  glues  from 
time  to  time,  "When  is  So  and  So  coming?  That  fellow 
understands  his  business  and  I  would  like  to  have  him 
assist  me  in  solving  a  very  perplexing  glue  problem." 
Truly,  the  salesman  who  can  do  these  things  is  tying 
his  customers  to  him  with  ropes  of  steel  and  will  make 
his  visits  an  event  instead  of  a  call. 

When  visiting  a  propect  endeavor  in  every  way 
to  obtain  samples  of  the  glues  he  is  using  and  mail 
these  promptly  to  your  factory  laboratories  for  analy- 
sis. The  factory  manager  should  insist  upon  having 
samples  tested  on  the  same  day  they  arrive,  or  as  soon 
thereafter  as  possible.  In  the  event  of  a  big  contract 
being  at  stake  and  there  being  a  likelihood  of  the  con- 
tract being  signed  within  a  very  few  days,  the  sales- 
man should  do  the  testing  at  the  prospective  place  of 
business.  Should  this  be  impossible,  make  a  few  im- 
portant tests  at  the  hotel.  I  would  suggest  the  carry- 
ing of  a  viscosimeter,  balance,  litmus  papers  and  a  few 
beakers.  The  jelly  can  in  such  extreme  cases  be  tested 
by  what  is  known  as  the  "finger  test"  fully  explained  in 
other  pages  of  this  book.  A  suitable  thermometer  can 
be  carried  in  the  vest  pocket,  in  fact,  it  is  as  necessary 
for  a  good  glue  salesman  to  carry  such  an  instrument 


THE   GLUE   SALESMAN 169 

as  it  is  for  the  physician.  Stick  (as  you  would  have 
your  glue  do)  until  you  have  closed  the  deal.  Remem- 
ber, you  are  in  a  sticky  line  so  never  say  "quit." 

If  you  want  to  reach  the  high  mark  in  the  selling  of 
glue,  you  have  to  have  overwhelming  belief  in  yourself 
and  not  only  in  the  glues  you  sell,  but  in  the  house  that 
manufactures  them,  and  you  must  believe  in  yourself 
first  of  all.  Extravagant  hope  and  confidence  are 
necessary.  This  is  one  place  where  extravagance  is  an 
asset. 

Enthusiasm  is  the  great,  far-reaching  wisdom  of 
faith — it  prompts  and  sustains  the  noblest  efforts.  If 
you  have  it  you  should  be  thankful  and  if  you  have  the 
brand  that  is  contagious,  you  are  a  public  benefactor 
and  a  record-breaker  so  far  as  sales  go.  Never,  Never, 
NEVER !  show  a  weakness  in  your  argument  or  gen- 
eral sales  talk,  for  this  will  be  detected  and  like  E 
enthusiasm,  is  contagious.  Do  not  because  a  man  buys 
tons  of  glue  every  year,  be  afraid  of  him  and  feel  more 
at  home  in  the  small  hardware  store  selling  probably 
twenty-five  pounds  annually.  Your  prospects  must 
never  be  approached  with  timidity,  an  "excuse-me-for- 
living"  attitude.  You  are  or  should  be  just  as  good  a 
man  as  the  purchasing  agent. 

One  grave  mistake  I  find  so  many  salesman  make, 
especially  men  representing  very  large  glue  factories, 
is  to  "jump  towns"  and  call  up  over  long  distance  tele- 
phone from  some  neighboring  city  and  say  in  a  seem- 
ingly bored  way :  "Went  through  your  town  this  after- 
noon, but  really  it  does  not  pay  me  to  stop  off  in  small 
cities,  for  you  know  I'm  representing  a  very  large  glue  01 
house  and  we  must  keep  moving.  Anything  doing  in 
the  glue  line  today?"  Such  men  are  not  salesmen,  but 
may  be  classed  as  mere  order  takers.  Of  course,  it 
may  at  times  be  necessary  to  resort  to  the  telephone, 
but  do  not  do  so  unless  it  is  absolutely  necessary  and 
you  are  very  well  acquainted  with  the  purchaser, 
knowing  that  he  will  not  be  offended. 

Don't  ignore  questions  about  competitors,  and  don't 
fail  to  banish  from  the  customer's  mind  all  doubts  and 
prejudices,  but  it  is  a  serious  mistake  to  spend  a  lot  of 


170 


MODERN  GLUES  AND  GLUE  TESTING 


COMPETITORS 


STRONG 
PERSONALITY 


time  talking  about  competitors'  glues  when  you  ought 
to  be  sticking  to  the  merits  of  your  own.  Answer 
quickly  all  questions,  and  then  switch  back  to  the  excel- 
lence of  your  product.  Be  so  enthusiastic  about  your 
own  selling  points  that  rivalry  will  be  forgotten.  In 
meeting  competition,  do  not  be  fooled  by  the  question 
of  price.  At  present,  very  many  lines  are  of  practically 
the  same  quality,  grades  considered,  and  prices  are 
about  the  same,  so  that  you  must  bring  out,  as  a  high 
grade  salesman  should,  the  fact  that  service  is  the 
main  consideration.  Show  what  your  house  can  do  in 
the  matter  of  prompt  deliveries,  careful  packing  of 
glues,  dependability  as  regards  uniform  quality, 
correct  weight,  liberal  terms,  etc.,  and  do  not  forget 
that  the  general  reputation  of  your  house  is  a  selling 
point.  The  facilities  which  you  have  for  keeping 
abreast  with  the  times,  like  the  employing  of  expert 
chemists  and  engineers  in  your  laboratories  to  do  your 
experimental  and  research  work,  thereby  improving 
the  quality  of  your  glues  all  the  time,  is  a  point  of  serv- 
ice well  worth  consideration. 

Above  all,  a  glue  salesman  can  meet  competition 
most  effectively  by  a  strong  personality.  Remember 
that  your  glues  are  judged  by  yourself,  sometimes 
even  unfairly;  and  remember  that  we  are  always 
judged  by  our  weakest  points;  hence,  in  order  to  hold 
your  trade  from  competitors,  and  to  get  new  trade, 
you  must  possess  what  is  commonly  called  "business 
magnetism,"  which  is  another  way  of  saying  a  strong 
personality. 

A  salesman  called  at  my  office  a  few  years  ago  clad 
in  a  "Prince  Albert"  coat,  very  delicate  kid  gloves,  a 
silk  hat,  highly  polished  patent  leather  shoes,  a  white 
tie,  a  large  diamnd  stud  and  his  fingers  were  decorated 
with  daimond  rings.  The  gentleman  had  the  appear- 
ance of  a  nobleman  and  when  he  handed  me  his  card 
which  stated  that  he  represented  a  glue  manufacturing 
concern,  I  was  astonished.  I  noticed  that  it  seemed  to 
actually  be  impossible  for  the  gentleman  to  talk 
because  of  a  very  high  starched  collar  he  was  wearing. 
It  occurred  to  me  that  it  would  be  cruel  to  expect  my 


THE   GLUE   SALESMAN 171 

new  acquaintance  to  say  anything  and  it  did  seem  that 
the  subject  of  glue  must  be  distasteful,  so  I  politely 
informed  his  excellency  that  we  are  not  considering 
new  glues.  I  kept  his  card,  however,  and  received  sam- 
ples from  time  to  time,  but  the  prices  were  so  high  as 
to  be  prohibitive.  It  evidently  cost  this  concern  money 
to  keep  the  dude  on  the  road. 

Another  instance  was  that  of  an  apparently  intelli- 
gent ^young  man  representing  a  prominent  glue  house, 
who  came  to  my  office  in  an  intoxicated  condition.  He 
fairly  staggered  to  my  desk  and  immediately  after  THE  "SPORT" 
introducing  himself  said  to  me  in  what  was  to  be  an 
undertone,  that  he  spent  the  night  in  Toledo  and  had  a 
h of  a  time.  Did  he  get  an  order? 

Again,  we  meet  the  type  of  salesman  who  knows  all 
about  glues.  He's  the  "candy  salesman."  No  one  has 
anything  on  him.  He  can  determine  glue  quality  by 
taking  the  lid  off  the  barrel  and  smelling  of  the  glue, 
or,  by  looking  through  the  flake  he  can  tell  the  grade.  THE  "EXPERT'' 
"Them  there  new  glue  testing  methods  ain't  no  good." 
Mr.  Wise  doesn't  care  what  tests  show,  he'll  tell  you 
that  it  takes  an  expert  like  himself  to  select  glues,  leave 
it  to  him,  he'll  supply  the  right  kind  of  stuff  and  save 
you  money. 

The  writer  met  a  glue  salesman  a  short  time  ago, 
who  complained  very  bitterly  about  not  being  appreci- 
ated and  the  low  salary  his  employers  are  paying  for 
his  services.  I  told  him  that  I  was  sorry  because  he 
imagined  his  employers  were  trying  to  keep  him  down ; 
that  I  know  the  concern  very  well  and  that  I  did  not 
believe  them  to  be  business  men  of  that  sort.  I  asked 
whether  he  ever  thought  of  how  much  money  he  was 
making  for  his  employers  ?  Did  he  make  many  mis-  THE  "CRAB" 
takes  and  get  the  concern  into  trouble  because  in  some 
cases  he  may  be  overly  anxious  and  make  statements 
that  cannot  be  fulfilled?  Did  he  spend  his  leisure  time 
in  studying  glue  problems  and  was  he  familiar  with 
the  testing  of  glues,  abuses,  etc.?  He  thought  a  few 
minutes,  then  replied,  "Guess  you  are  right,  have  never 
thought  of  my  position  just  that  way."  I  hope  the 
young  man  in  question  reads  this  book  and  especially 


172 


MODERN  GLUES  AND  GLUE  TESTING 


TRAIK    YOUR 
SALESMEN 


REGARDING 
ADVERTISING 


this  paragraph.  He  is  invited  to  write  to  mo  and  to 
state  whether  my  suggestions  have  proven  of  benefit  to 
him,  providing,  of  course,  he  has  followed  them. 

Glue  manufacturers  are  largely  to  blame  for  select- 
ing some  men  to  sell  glues  who  are  no  more  fitted  for 
this  vocation  or  profession  than  is  the  writer  to  drive 
an  airplane.  Indeed,  of  all  the  elements  which  go  to 
make  up  a  successful  glue  business,  that  of  salesman- 
ship is  most  frequently  neglected.  Business  is  a  profes- 
sion and  a  science.  Salesmanship,  which  is  a  direct  rep- 
resentation and  most  important  factor  in  business,  is 
the  greatest  of  all  professions,  and  is  likewise  a  science. 
If  some  of  you  glue  manufacturers,  jobbers  and  dealers 
could  watch  some  of  the  representatives  I  have  met 
trying  to  sell  glue,  you  would  be  tempted  to  boot  them 
out  of  the  office.  Do  not  in  the  name  of  common  sense 
regard  salesmen  as  necessary  evils.  Train  them  and  do 
not  permit  any  one  of  them  to  present  your  cards  to  the 
trade  nor  announce  their  connection  with  your  concern 
until  you  have  every  reason  not  to  be  ashamed  of  them. 

Instruct  your  salesmen  to  base  their  selling  cam- 
paign on  the  objections  that  are  sure  to  be  raised.  No 
salesman  should  ever  start  out  without  first  having 
satisfactorily  answered  every  conceivable  objection 
from  every  point  of  view. 

It  is  singular,  indeed,  to  observe  so  few  advertise- 
ments from  glue  manufacturers.  Some  will  tell  you 
that  the  reason  they  do  not  advertise  is  because  they 
employ  salesmen  whose  business  it  is  to  call  on  pros- 
pectives  and  customers,  show  samples  of  glues  and 
discuss  their  merits.  The  glue  manufacturer  seems  to 
forget  that  through  the  advertisement  published  in 
good,  live  trade  journals  he  will  reach  thousands  of 
glue  users  at  nearly  the  same  time  and  the  salesman 
can  call  on  but  one  person  at  a  time.  It  is,  of  course, 
true  that  the  advertisement  may  not  always  complete  a 
sale,  but  it  will  certainly  pave  the  way  for  future  busi- 
ness, for  it  will  impress  the  name  or  an  attractive  qual- 
ity so  that  the  reader  will  think  of  your  concern  when 
in  the  market  for  glues.  A  good  ad  will  invariably 
influence  the  reader  in  favor  of  your  commodity. 


THE   GLUE   SALESMAN  173 

The  writer  has  heard  glue  makers  say:  "Why 
should  I  advertise?  Supposing  I  list  grades  of  glues 
based  on  Peter  Cooper  standards;  I  name  prices 
and  some  competitor  will  answer  my  ad  stating  that 
he  is  prepared  to  offer  lower  prices.  He  will  not  fur- 
nish the  same  grades,  but  too  few  glue  users  test  glues 
and  would  be  unable  to  tell  the  difference,  so  I  lose  out 
because  of  being  honest  and  the  trickster  gets  the  busi- 
ness." The  writer  must  admit  that  this  has  been  true, 
but  we  must  also  remember  that  we  are  all  doing  busi- 
ness differently  than  we  did  five  or  ten  years  ago. 
Where  such  a  condition  exists  it  is  the  best  kind  of  ad- 
vertising to  show  up  the  cheater  and  by  so  doing  the 
glue  buyer  will  be  your  friend  for  life. 

Many  glue  manufacturers  are  doing  a  great  deal  of 
effective  advertising  by  means  of  form  letters,  which 
are  printed  in  imitation  of  typewriting.  Indeed,  some 
of  the  very  best  form  letters  I  have  ever  perused  were 
written  by  some  genius  who  certainly  understood  the 
requirements  of  glue  users  and  his  letters  without  a  FORM 
doubt  "brought  home  the  bacon."  At  the  present  time  LETTERS 
printing  offices  in  nearly  all  of  the  large  cities  can  fur- 
nish form  letters  from  typewriter  type  that  are  good 
imitations  of  typewriting.  Good  matching  is  very  im- 
portant in  inserting  names,  addresses,  and  other  mat- 
ter in  form  letters. 

Glue  advertisers  can  sometimes  afford  to  distribute 
novelties  that  will  keep  their  names  before  the  public. 
I  often  wondered  why  manufacturers  do  not  prepare 
printed  tables  for  the  glue  buyer  showing  viscosity 
test,  jelly,  etc.  It  would  certainly  be  splendid  to  pre- 
pare tables  from  different  strength  solutions  run 
through  various  viscosimeters,  especially  the  viscosi- 
meter  having  various  sized  apertures.  Again,  inex- 
pensive thermometers  for  the  glue  room  would  be 
appreciated.  These  novelties  would  likely  not  bring 
direct  sales,  but  would  support  other  advertisements 
together  with  the  work  done  by  your  salesmen.  Your 
novelty  should  be  a  constant  reminder  of  your  business 
and  should  be  of  such  value  so  it  will  not  be  destroyed. 


CHAPTER  XXVIII. 

BUYING  AND  SELLING  GLUE. 

THE  functions  of  every  purchasing  department  in 
a  manufacturing  establishment  are:     First — To 
secure  the  most  satisfactory  material  required  in 
the  manufacturing  processes.    Second — To  secure  the  DUTIES  OF 
most  desirable  delivery  of  the  material,  keeping  com-  PURCHASING 
plete   and   accurate   record   of   all   unfilled   purchase  DEPARTMENT 
orders. 

Third — To  obtain  the  best  terms  of  payment  and 
the  lowest  prices,  quality  considered. 

Fourth — To  record  and  classify  materials  and  sup- 
plies used  and  purchases  made. 

Fifth — The  buyer  should  have  complete  lists  of  all 
manufacturers  of  glues  and  other  adhesives.  He  should 
keep  in  touch  with  these  concerns  and  though  he  can- 
not buy  from  all,  and,  would  possibly  buy  but  from  one 
or  two,  nevertheless,  it  is  well  to  receive  quotations  and 
sSamples  for  comparison. 

The  successful  accomplishment  of  the  first  function 
demands  that  the  glue  buyer  shall  be  a  man  who  has  a 
working  knowledge  of  the  particular  industry  for 
which  he  is  buying  this  class  of  material.  If  he  has  in 
addition  acquired  the  knowledge  of  glue  testing,  so 
much  the  better,  for  he  will  be  able  to  make  practical 
application  of  such  knowledge. 

If  care  is  exercised  to  obtain  a  man  of  the  qualifica- 
tions indicated  to  purchase  glue,  there  will  be  far  less 
liability  to  make  the  error  so  frequently  made,  of  buy- 
ing grades  of  glues  good  enough  in  themselves,  but  not 
exactly  adapted  to  the  particular  purpose  for  which 
the  glue  is  desired. 

The  second  function  applies  largely  to  the  traffic 
department,  or,  in  small  plants  proper  routing  should 
be  specified  by  the  glue  buyer.  Again,  it  is  usually  im- 
portant to  ascertain  at  the  time  of  purchasing  the  age 
of  the  glue  and  the  possible  date  of  shipment. 

To  obtain  the  lowest  price  does  not  mean  "cheap 


176 


MODERN  GLUES  AND  GLUE  TESTING 


SUBSTITUTING 
PRICE  FOR 
QUALITY 


TRAY   CARDS 


glue."  It  is  to  be  regretted  that  in  too  many  cases  glue 
is  considered  as  just  glue.  Some  salesmen  fear  compe- 
tition and  have  no  desire  to  enlighten  the  glue  buyer  as 
to  glue  standardizing.  The  tendency,  therefore,  is  for 
the  salesman  to  say  that  his  glue  is  as  good  or  stronger 
than  the  one  the  buyer  is  using,  that  it  takes  more 
water  and  as  a  natural  consequence  is  a  cheaper  prod- 
uct so  far  as  glue  economy  is  concerned.  The  salesman 
may  make  price  the  predominating  element,  to  substi- 
tute salesmanship  for  science.  High  grade  glue  costs 
money  and  no  manufacturer  can  afford  to  sell  an 
article  for  fifty  cents  that  possibly  costs  him  one  dollar 
to  produce  in  his  factory.  Nevertheless,  prices  may  be 
unreasonably  higher  and  the  buyer  should  possess  the 
ability  to  determine  the  lowest  just  and  fair  price,  the 
quality  of  the  material  considered. 

It  is  well  to  list  manufacturers,  jobbers  and  dealers 
selling  glue  on  suitable  tray  cards.  The  card  should 
give  the  name  of  the  manufacturer,  jobber  or  dealer, 
address,  grades  of  glues  manufactured,  financial  rating 
(the  financial  rating  being  a  fairly  good  barometer  to 
show  whether  or  not  the  manufacturer,  jobber  or 
dealer  is  financially  able  to  carry  out  the  terms  of  the 
crder  of  contract.)  The  card  should  also  show  the  kind 
of  glue  manufactured,  hide,  bone,  vegetable,  water- 
proof or  any  other  adhesive.  The  buyer  should  ascer- 
tain, if  possible,  what  grades  of  glues  the  manufac- 
turer, jobber  or  dealer  specializes  in.  The  manufac- 
turer of  paper  boxes  would  likely  not  be  interested  in 
high  grade  hide  glues  and  the  wood  worker  would  not 
find  the  box-maker's  glue  practical  in  his  line  of  work, 
therefore,  it  would  not  be  advisable  to  list  all  grades  of 
glues  and  the  manufacturers,  jobbers  or  dealers  handl- 
ing the  grades  and  kind  of  glues  you  do  not  require. 

The  back  of  this  card  may  be  arranged  in  columns 
for  the  purpose  of  entering  quotations.  The  first  col- 
umn would  show  the  date,  the  second  manufacturer's 
or  jobber's  number  of  the  glue  boiling;  the  third,  grade 
of  glue;  fourth,  the  number  of  unsold  pounds  in  the 
boiling;  fifth,  F.  0.  B.  point;  sixth,  price;  seventh, 
terms.  Ordered  columns  may  also  be  provided  on  the 


BUYING  AND   SELLING  GLUE  177 

back  side  of  the  card.  First  column  showing  the  date 
and  second,  quantity  ordered. 

The  glue  buyer  must  insist  upon  receiving  timely 
requisitions  from  all  the  departments  requiring  glue. 
Under  ordinary  circumstances  the  purchaser  of  glues  REQUJSITIONS 
should  place  no  orders  until  he  has  first  received  a  REQUn 
requisition  from  either  the  stores  department  or  the 
department  that  requires  material. 

A  positive  rule  should  be  laid  down  that  all  glue 
requirements  be  anticipated  in  ample  time  so  that  the 
buyer  will  not  be  compelled  to  purchase  unsatisfactory 
stock  from  possibly  a  nearby  dealer  so  as  to  avoid  a 
"shut-down."  Again,  requisitions  should  be  signed  or 
countersigned  by  either  the  foreman  requiring  the  ma- 
terial or  the  superintendent.  Requisitions  can,  of 
course,  be  drafted  to  meet  individual  requirements. 

When  contracts  are  made  involving  a  large  invest- 
ment, considerable  testing  and  investigating  will  be 
necessary  and  the  writer's  experience  has  been  that  it 
will  require  from  thirty  to  sixty  days  to  get  samples, 
test  them,  receive  quotations  and  finally  decide  upon 
the  glue  that  will  be  contracted  for.  •  . 

Departments  requiring  glue  or  store  rooms  should 
carry  what  may  be  termed  a  "Low  Stock  Report."  The 
glue  should  be  given  a  low  limit  and  when  this  is 
reached  the  workmen,  foreman,  stores-keeper  or  who- 
ever has  charge  of  the  glue  should  report  promptly  to 
the  person  issuing  the  requisitions. 

It  is  also  imperative  to  keep  a  complete  record  of  all 
tests  and  to  file  them  for  future  reference.  A  vertical 
two-drawer  bill  file  cabinet  answers  this  purpose  very 
nicely.  In  the  top  drawer  file  favorable  reports.  In  the 
second  drawer  the  unfavorable.  The  advantage  of  this  KEEP  A 
scheme  is  apparent,  for  it  is  a  simple  matter  to  deter-  RECORD  or 
mine  within  a  few  moments  who  supplied  the  best  and  TESTS 
who  the  poorest  samples.  All  test  cards,  good  or  poor, 
should  be  filed.    I  have  found  this  scheme  especially 
valuable  in  calling  the  bluffs  of  glue  salesmen  who  per- 
sist in  knocking  their  competitors'  glues. 

The  manufacturer  spending  money  in  the  way  of 
the  salesman's  salary,  railroad  and  hotel  expenses  de- 


178 


MODERN  GLUES  AND  GLUE  TESTING 


GIVE  THE 
SALESMAN 
A  CHANCE 


serves  consideration.  It  is  to  be  regretted  that  many 
glue  buyers  do  not  appreciate  this  and  in  many  cases 
glue  salesmen  representing  the  most  successful  and 
reliable  glue  houses  are  turned  down — not  even  given 
an  audience.  When  a  salesman  spends  time  and  money 
to  visit  you,  he  has  something  to  say  and  if  you  are  a 
good  buyer  you  will  permit  him  to  have  his  say.  To  be 
sure  there  are  many  men  who  suppose  the  buyer  has 
no  other  duties  than  to  listen  to  stories,  smoke  cigars, 
and  be  a  good  fellow.  The  writer  usually  allowed  every 
salesman  from  five  to  ten  minutes  and  he  was  given  to 
understand  when  entered  my  office  that  he  must  be 
brief. 

Another  suggestion:  Whenever  you  find  a  boiling 
that  is  highly  satisfactory,  buy  the  entire  boiling.  Of 
course,  the  writer  appreciates  that  small  manufactur- 
ing plants  cannot  at  all  times  avail  themselves  of  such 
offerings,  however,  the  glue  manufacturer  may  reserve 
a  certain  quantity  or  possibly  all  of  the  boiling  for  the 
small  manufacturer,  especially  so  if  a  reasonable  de- 
posit is  made  or  a  liberal  amount  taken  in  on  the  first 
shipment.  When  buying  the  entire  boiling  you  know 
absolutely  just  what  you  are  receiving.  The  writer 
has  never  regretted  doing  this. 

If  the  buyer  of  glues  will  avail  himself  of  the  infor- 
mation given  he  will  avoid  excessive  buying,  inferior 
quality,  high  prices  and  poor  deliveries.  Right  buying 
means  an  improvement  in  the  quality  of  the  goods, 
increased  production,  and,  last  but  by  no  means  least, 
satisfied  customers. 


CHAPTER  XXIX. 

PAPER  BOX  ADHESIVES. 

THE  average  paper  box  manufacturer  buys  very 
cheap  glue.    This  is  usually  a  bone  product  of  the 
lowest  grade.    It  is  possible  to  use  almost  any 
kind  of  glue  in  the  manufacture  of  paper  boxes  and  the 
real  factor  is  the  price.   It  is,  of  course,  imperative  to 
select  glues  that  are  not  in  the  stages  of  decomposition 
and  the  tests  explained  in  this  book,  when  properly 
applied,  are  all  the  information  that  is  required  to 
determine  this  point.  Again,  in  boxes  that  are  printed  m 

i  i     ..      •  •  -i         -i  i-ii  br*L,LCTlO,N    OF 

or  colored  it  is  necessary  to  avoid  glues  that  are  too  GLUE  FQR 
strongly  alkali  or  acid.  The  litmus  tests  explained  for  PAP 
acidity  or  alkalinity  must  be  applied.  If  the  paper  box 
maker  will  study  all  the  information  explained  in  the 
pages  of  this  treatise  he  will  eliminate  all  of  his  glue 
troubles.  It  will  be  appreciated  that  it  takes  but  little 
glue  room  abuse  to  almost  destroy  the  adhesiveness  of 
a  cheap  or  low  grade  glue.  Watch  the  temperature. 
When  heated,  all  glues  are  gradually  killed  and  the 
damaging  action  begins  as  soon  as  the  temperature  of 
the  solution  reaches  120  degrees.  Unfortunately  a 
slightly  higher  temperature  than  the  temperature  at 
which  damage  to  glue  begins  is  quite  necessary,  never- 
theless, common  sense  must  enter  into  the  problem 
and  if  the  paper  box  makers  will  exercise  great  care 
they  can  obtain  a  higher  degree  of  efficiency  and  in 
many  cases  greatly  improve  the  quality  of  their 
product. 

The  novice  will  be  surprised  to  observe  the  possi- 
bilities of  box  making  machines.   There  are  a  number 
of  popular  machines ;  we  will,  however,  discuss  the  B0x  MAKING 
merits  of  but  three.  MACHINES 

The  Jagenbry  Box  Making  Machine  automatically 
feeds  the  cut  out  blanks,  forms  the  box,  glues,  applies, 
cuts  strip  paper  and  turns  striper  in  and  over. 

The  Staude  Automatic  Folding  Box  Gluer  will  auto- 
matically feed  blanks  one  at  a  time  at  a  high  speed, 


180 


MODERN  GLUES  AND  GLUE  TESTING 


ESSENTIAL 
REQUIREMENTS 


SILICATE  OF 
SODA 


glue,  fold,  count  and  stack  in  a  vertical  pile  that  keeps 
the  glued  seam  under  pressure  so  it  cannot  pop  open. 

There  is  a  possibility  of  combining  vegetable  and 
mineral  adhesives  such  as  starch  solutions  and  flour 
pastes  and  silicate  of  soda.  The  essential  requirements 
would  here  be  that  the  vegetable  part  should  not  con- 
tain any  considerable  excess  of  free  alkali. 

Most  box  makers  have  their  own  private  formulas. 
One  of  the  points  to  remember  when  working  out  a 
formula  for  a  paper  box  adhesive  is  the  setting  of  the 
glue.  Of  course,  we  know  that  the  lower  the  tempera- 
ture in  the  work-room  the  lower  the  temperature  of 
the  warm  liquid  glue,  and  the  higher  the  grade  of  the 
glue,  the  quicker  will  the  glue  set. 

For  the  building  of  chip  or  container  board  silicate 
of  soda  is  used.  The  stock  is  built  up  the  same  as  ply- 
wood. The  only  pressure  applied,  however,  is  on  the 
machine  when  the  stock  goes  through  the  squeeze  rolls. 
Silicate  of  soda  has  much  less  water  in  it  than  is  used 
with  other  adhesives  and  the  various  grades  are  pro- 
duced with  considerable  latitude  in  setting. 

It  requires  from  fifteen  to  twenty  pounds  of  silicate 
to  build  up  1,000  square  feet  of  three-ply  board,  15 
pounds  as  minimum  and  20  pounds  as  maximum.  It 
varies  between  these  two  points  on  different  grades  of 
paper.  Each  additional  ply  will  require  from  71/2  to  10 
pounds  additional  silicate  of  soda.  A  three-ply  board 
has  two  pasted  sides.  A  four-ply  board  has  three 
pasted  sides,  each  side  requiring  7l/9  to  10  pounds  of 
silicate  of  soda  per  1,000  square  feet  irrespective  of 
caliper  of  the  board. 

Silicate  of  soda  is  packed  in  either  wooden  barrels 
or  metal  drums,  both  containing  approximately  600 
Ibs.  The  barrels  have  two  openings,  one  in  the  center 
and  one  in  the  head,  and  the  silicate  can  be  drawn  from 
the  same  with  a  good  sized  spigot,  say  one  inch  inside 
opening.  The  user  should  always  draw  from  the  barrel 
in  a  small  container  the  desired  amount  for  one  day's 
use,  and  when  the  brush  is  not  in  use  the  bristles 
should  be  submerged  in  water,  which  will  preserve 
them. 


CHAPTER  XXX. 


AVOID  ABUSES. 


EVERY  office  and  department  in  any  manufactur- 
ing plant  requires  system  and  organization. 
When  these  important  factors  are  neglected  the 
quality  of  the  goods  is  certainly  compelled  to  suffer  and 
the  manufacturer  usually  realizes  a  loss  instead  of  a 
gain.  No  manufacturer  is  in  business  for  his  health. 
He  cannot  "break  even"  year  after  year  and  he  is 
either  making  or  losing  money.  The  woodworking 
manufacturer  knows  that  it  costs  money  to  repair  open 
joints  or  blistered  and  loose  veneers.  It  isn't  always 
the  fault  of  the  glue,  as  has  been  generally  charged, 
and  I  know  from  experience  that  in  most  cases  the 
workmen  or  the  system  are  at  fault.  Our  first  duty  is 
to  select  the  grade  or  grades  of  glue  that  will  give 
reliable  results.  When  selecting  glue  for  wood  work 
we  must  insist  upon  receiving  the  purest  glue  avail- 
able, glue  that  is  not  loaded  with  chemicals  to  give 
fictitious  value.  The  writer  has  already  explained  the 
requirements  of  various  lines  and  we  will  not  here 
repeat  anything  that  has  been  stated. 

It  is  immaterial  whether  we  manufacture  matches, 
emery  wheels,  cloth,  paper  boxes,  furniture,  caskets, 
pianos,  etc.  We  are  all  interested  in  glue  that  holds.  It 
is  an  absolute  fact  though  that  different  workmen  may 
get  different  results  with  the  same  glue  all  made  in  one 
boiling  at  the  glue  factory.  Why  such  differences  ?  The 
answer  is  simply,  that  every  one  of  the  men  may  abuse 
the  glue,  one  more  than  the  other  and  when  used  the 
quality  is  not  the  same  high  grade  as  when  originally 
dropped  in  the  glue  cooker. 

The  one  feature  that  is  an  absolute  essential  to  the 
proper  working  or  handling  of  glue  is  intelligence.  We 
want  to  forget  that  any  Tom,  Dick  or  Harry  can  pre- 
pare glues,  and  all  you  need  give  him  is  a  few  pails,  a 
quantity  of  glue  and  show  him  where  the  faucet  is  so 
that  he  can  prepare  the  glue  for  "soaking."  We  must 


RESULTS 


182 


MODERN  GLUES  AND  GLUE  TESTING 


LET  YOUR 
MEN  READ 
THE  BOOK 


GLUE    ROOM 
TEMPERATURE 


train  our  men,  and  to  do  so  every  manufacturer,  large 
or  small,  can  well  afford  to  place  our  glue  books  in  the 
various  departments  so  that  the  workmen  can  learn 
how  glue  should  be  prepared  and  properly  handled  to 
get  100%  efficiency.  The  workmen  who  master  all  this 
book  contains  may  rightly  call  themselves  experts,  and 
if  this  is  done  the  manufacturer  will  then  have  the 
assurance  that  glue  room  troubles  are  a  thing  of  the 
past.  I  did  not  incorporated  this  statement  to  boost  the 
sale  of  the  book,  but  this  is  absolute  truth  and  the 
writer  has  in  mind  only  the  welfare  of  his  readers. 

Practically  every  department  in  a  manufacturing 
plant  has  one  or  more  foremen.  These  men  are  singled 
cut  to  oversee  the  work.  This  should  also  be  done  in 
the  glue  room.  Single  out  the  most  intelligent  man  you 
have  in  that  department  and  hold  him  responsible. 
This  need  not  be  the  foremen  for  the  reason  that  these 
men  have  too  many  details  and  they  likely  cannot  give 
the  preparation,  distribution  and  using  of  the  glues  the 
close  and  careful  attention  so  necessary  if  quality  is  to 
be  realized. 

Proper  equipment  is  very  necessary.  We  are  going 
to  discuss  equipment  in  another  chapter  so  will  next 
direct  your  attention  to  the  temperature  of  the  glue 
room.  We  all  know  how  imperative  it  is  to  have  a 
fairly  uniform  temperature  in  varnish  rooms.  Your 
glue  room  is  just  as  important.  Again,  you  avoid  draft 
in  the  varnish  room  and  we  must  do  so  in  the  glue 
room.  Chilled  glue  will  cause  trouble  and  when  the 
stock  is  too  hot,  owing  to  a  very  high  temperature  in 
the  gluing  department,  the  men  are  uncomfortable. 
Some  men  insist  upon  heating  the  wood  until  so  hot 
that  one  cannot  touch  the  heated  surface  with  the 
naked  hand.  When  wood  is  heated  hot,  too  much  glue 
is  taken  up.  Then  when  the  wood  cools  off  the  air  in 
the  pores  beneath  the  glue  contracts  as  it  cools,  creat- 
ing a  suction  which  draws  the  glue  farther  into  the 
wood,  and  this  is  liable  to  seriously  affect  the  joint  for 
there  may  be  a  little  glue  left  on  the  surface,  as  it  is  all 
absorbed  by  the  wood. 

Having  the  ideal  glue  room  conditions  and  the  most 


AVOID   ABUSES 183 

suited  stock  for  our  peculiar  requirements,  we  must 
measure  the  glue  and  water.    Hundreds  of  manufac- 
turers in  all  lines  of  business  neglect  doing  this  and  the 
men  pour  water  on  the  dry  glue  until  the  surface  has  GLUE  AND 
been  covered.    Weigh  your  water  as  well  as  the  glue  WATERMUST 
and  watch  the  proportions  very  carefully.  BE  WEIGHED 

The  function  of  soaking  is  to  get  back  into  the 
glue  the  liquid  it  originally  contained.  Precautions 
must  be  observed  that  will  insure  uniform  softening 
prior  to  melting.  Very  frequently  one  finds  long  or 
wide  flakes.  It  is  well  to  break  them  into  suitable  sizes 
prior  to  soaking.  Do  not  permit  pieces  to  stick  out  of 
the  water.  All  of  the  glue  must  soak  and  unless  this 
is  the  case  it  will  take  a  considerably  longer  time  to 
melt  than  if  soaked  properly  before  applying  heat. 
Many  so-called  "glue  experts"  object  to  soaking  the 
glue  over  night.  This  is  perfectly  right  in  the  case  of 
flake  glues,  providing,  of  course,  the  room  is  not  too 
hot.  Hot  summer  nights  are  not  very  desirable.  Glues 
should  not  be  soaked  too  long  as  too  much  soaking  kills 
the  strength.  Thin  cut,  high-test  glues  absorb  water 
rapidly.  They  will  therefore  soak  in  a  much  shorter 
time  than  thick  glues.  This  applies  as  well  to  ground 
glues.  A  very  good  plan  is  to  pour  water  (taken  from 
the  quantity  weighed)  into  the  soaking  container  so 
that  when  adding  the  glue  it  will  surely  become  soaked. 
Unless  this  is  done  you  are  taking  chances  and  there 
may  be  particles  or  flakes  at  the  bottom  that  will  not 
become  saturated.  Stir  again  and  again.  This  will 
assist  very  much  and  will  to  some  extent  shorten  the 
time  of  the  soaking. 

Use  only  pure,  cold  water.    Some  men  seem  to  be 
under  the  impression  that  there  is  no  better  water 
than  that  which  has  been  chemically  treated  in  the 
boiler  for  the  prevention  of  scale.    The  writer  at  one 
time  visited  a  woodworking  plant  having  consider-  DO  NOT  USE 
able  trouble  with  glue.    The  grade  was  splendid,  the  BOILER 
men  did  not  appear  to  overheat  it  and  the  entire  prob-  WATER 
lem  had  me  guessing  until  I  saw  a  workman  coming  up 
the  stairs  with  two  pails  of  water.    I  immediately  be- 
came suspicious,  and  asked  him  for  what  purpose  he 


184 


MODERN  GLUES  AND  GLUE  TESTING 


CORRECT  HEAT 


GLUE    ROOM 
EQUIPMENT 


intended  the  water.  He  replied,  to  soak  the  glue.  I 
said,  "Haven't  you  water  faucets  in  your  glue  room?" 
He  replied,  "The  clearest  water  we  can  possibly  get  is 
water  that  has  been  softened  and  this  comes  from  the 
boiler."  Here  was  the  answer. 

Again,  I  observed  men  drawing  water  from  the 
water  jacket  in  the  glue  cooker.  This  sort  of  thing  is 
inexcusable  and  should  not  be  tolerated  in  any  glue 
room. 

We  have  perused  hundreds  of  articles  in  trade 
papers  dealing  with  the  subject  of  overheating  glues. 
Every  salesman  cautions  us  against  this  evil.  We  feel, 
therefore,  that  little  information  is  necessary  along 
this  line.  However,  for  the  benefit  of  any  reader  who 
may  not  know  what  damaging  effects  heat  has  on  glue, 
I  want  to  state  that  the  most  desirable  temperature  to 
heat  glue  is  approximately  148  degrees  F.  For  some 
classes  of  work  from  138  up  to  145  is  perfectly  safe. 

The  moment  a  mixture  of  glue  and  water  is  heated 
enough  to  melt  it  a  gradual  change  begins  to  take  place 
in  such  a  way  that  the  water-taking  or  spreading  capa- 
city of  the  glue  is  gradually  destroyed.  It  is  caused  by 
the  water  attacking  the  glue  and  heat  increasing  the 
effect  of  the  attack. 

Heat  should  be  applied  indirectly.  That  is,  do  not 
permit  steam  to  come  in  direct  contact  with  the  glue. 
Open  iron  kettles  should  never  be  employed.  Of  course, 
there  is  always  more  or  less  evaporation  in  glues.  How- 
ever, if  the  cookers  or  glue  pots  are  closed  this  evapo- 
ration would,  to  a  great  extent,  be  eliminated.  The  con- 
struction of  the  glue  cookers,  pots,  tanks,  etc.,  is  there- 
fore of  great  importance.  Our  grandfathers  would 
work  with  open  iron  kettles.  Shavings,  sawdust  and 
foreign  matter  would  be  conspicuous  in  the  glue  pots. 
Therefore,  they  found  it  necessary  to  add  more  dowels 
or  drive  more  nails  to  assist  the  glue  in  holding  than  is 
necessary  today.  We  could,  of  course,  go  into  details 
regarding  cookers.  However,  there  are  a  number  of 
very  good  dissolvers  or  commonly  called  "glue  cook- 
ers," on  the  market  and  every  manufacturer  makes 
certain  claims  for  his  product.  The  writer  suggests 


AVOID   ABUSES 185 

though  that  the  buyer  be  very  careful  and  that  he  buy 
only  such  glue  room  equipment  as  will  give  lasting 
results. 

The  equipment  being  right,  there  should  be  no 
trouble  upon  obtaining  a  uniform  melt  at  the  minimum 
temperature. 

You  would  not  think  of  operating  your  boilers 
without  water  and  steam  gauges.  Therefore,  it  is  im- 
perative that  you  provide  thermometers  to  your  cook- 
ers, glue  pots  and  glue  spreaders.  The  automatic  tem- 
perature controller  is  a  wonderful  appliance  and  by  its 
use  the  supply  of  heat  is  automatically  regulated. 

When  melting  do  so  slowly.  Every  experienced  glue 
user  knows  that  there  is  nothing  to  be  gained  by  at- 
tempting to  dissolve  the  glue  within  a  few  minutes  and  MELT  QLUE 
that  when  this  is  attempted  a  scum  is  formed  over  the  SLOWLY 
glue,  preventing  its  proper  melting. 

It  is  well  to  prepare  two  or  three  batches  a  day  or 
more  if  necessary.  Do  not  prepare  so  great  a  quantity 
that  enough  glue  is  dissolved  to  last  three  or  four  days. 
A  glue  solution  when  allowed  to  cool  and  then  is  re- 
melted  has  not  the  same  tenacity  as  a  freshly  prepared 
solution.  Consequently,  for  ordinary  work,  the  quan- 
tity of  glue  solution  prepared  should  not  be  more  than 
is  required  for  immediate  use. 

The  melting  pots  should  be  kept  perfectly  clean. 
Much  unnecessary  waste  may  be  avoided  through  ob- 
servance of  cleanliness.  After  the  melted  glue  becomes 
sour,  and,  unless  this  sour  glue  has  been  removed  from 
the  melting  pot  it  will  spoil  the  fresh  solution.  Do  not, 
therefore,  tolerate  dirty  pots  and  do  not,  under  any 
circumstances,  mix  or  permit  a  mixture  of  old  dis- 
solved and  new  glue. 

Again,  do  not  permit  glue  to  freeze.  If  glue  jelly  is 
frozen  through  it  will  crumble  and  act  about  like  over-  ^  NOT  ALLOW 
heated  glue. 

Do  not  use  the  glue  until  it  has  thoroughly  melted. 
So  many  glue  users  seem  to  labor  under  the  impression 
that  partly  dissolved  glue  can  be  used  with  perfect 
safety.  This  is  wrong  and  should  not  be  put  into 
practice. 


186      MODERN  GLUES  AND  GLUE  TESTING 

Do  not  permit  the  temperature  of  the  glue  to  raise 
or  lower.  Keep  it  uniform. 

Store  glue  in  a  dry  place  and  do  not  unhead  the 
barrels  until  you  are  ready  to  use  the  glue. 

Co-operation  is  absolutely  necessary  in  every  line 
of  business,  and  in  every  department.   Your  men  will 
be  glad  to  co-operate  if  given  a  chance.    Having  per- 
fected your  organization  so  that  you  know  absolutely 
that  you  are  receiving  100%  glue  room  efficiency,  do 
not  forget  the  men  who  are  assisting  you  in  making 
this  possible,  and,  the  men  who  are  actually  doing  the 
CO-OPERATE         work.    When  yoyr  men  are  doing  good  work,  be  big 
WITH  YOUR        enough  to  go  to  them  and  tell  them  so.  This  requires  a 
MEN  little  giving  on  the  part  of  the  employer,  superinten- 

dent or  foreman,  but  it  is  no  expense — it  is  merely  the 
giving  of  credit  where  it  is  due.  As  your  men  improve 
in  your  service  their  incomes  should  improve.  The  pay 
envelope  and  the  occasional  word  of  commendation  are 
powerful  tools  that  you  have  at  your  command  for  a 
persistent  sequence  of  growth  toward  a  better 
business. 


MODERN  GLUES  AND  GLUE  TESTING 187 

MEMORANDA 


188 MODERN  GLUES  AND  GLUE  TESTING 

MEMORANDA 


MODERN  GLUES  AND  GLUE  TESTING 189 

MEMORANDA 


190 MODERN  GLUES  AND  GLUE  TESTING 

MEMORANDA 


MODERN  GLUES  AND  GLUE  TESTING 191 

MEMORANDA 


192  MODERN  GLUES  AND  GLUE  TESTING 

MEMORANDA 


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